What is the most fuel efficient highway drive speed?
Posted by Humble_Handler93@reddit | askcarguys | View on Reddit | 371 comments
Basically for the next few weeks to months I’m going to have to commute about 200 miles 5 days a week. I’m wondering what is the best speed to drive to maximize fuel economy on the highway. It’s open road driving with no traffic so I can set my cruise control from basically the moment I get in the highway till I get to my destination. I’m not sure if it matters but I drive a 6 cylinder 02 Avalon.
inspektor31@reddit
I like the lowest rpm in the highest gear. That’s for flat terrain though.
akluin@reddit
That's not about speed but rpm, being the lower rpm without being too low will give you the best efficiency
AwarenessGreat282@reddit
Often times, it's a certain RPM based on the engine. But going the slowest the law allows should be the most efficient. Looks like you have plenty of opportunity to find out though.
LITTELHAWK@reddit
Minimum speeds are often 45mph, which is usually worse efficiency than doing 65.
AwarenessGreat282@reddit
And you would be wrong. Time? Oh yes, much quicker. But not fuel efficiency.
LITTELHAWK@reddit
The issue I had when trying to do 45 mph was that it was at the bottom of the power band, so every incline would result in a downshift. 45 might be great somewhere that is perfectly flat, but I don't have that.
outline8668@reddit
With the scanner hooked up I have never seen a vehicle return worse mpg at 45 than at 65. Real question is who can drive 45 without getting run over?
kilroy-was-here-2543@reddit
If I go the speed limit on certain mountain roads near me I’ll actively be lugging the engine (getting less fuel economy than I would if sped up ) because the ECU likes to be a pain in the fucking ass.
AwarenessGreat282@reddit
A "lugging" engine is not burning more fuel. Lugging usually means lower RPM which means less fuel burned.
kilroy-was-here-2543@reddit
Yes it’s running at a lower RPM, but it’s working much harder than it should, and being less efficient while doing so
Essentially imagine putting your bicycle in the smallest gear and trying to pedal up a steep hill. Sure you’re not pedaling very fast, but you’re working very hard (and burning a lot more energy) doing so. Now go to a taller gear, and start pedaling. Sure you’re now pedaling faster, but your load is lower so you can burn less calories, your in your power band.
When you lug an engine you’re making it pedal much harder up that hill than it needs to. Made worse by the fact that as you lug longer you build up heat and start detonating gas making it even less efficient and also putting quite a bit of stress on the engine
AwarenessGreat282@reddit
Still doesn't burn any more fuel, just slows you down. Think of the shift lights in a manual tranny. They always came on early and the engine lugged when shifted at that point. They were programmed that way to return the best mpg, not performance.
kilroy-was-here-2543@reddit
I don’t know what car would have shift lights outside of a performance car, which case it’s definitely not focused on getting you the best efficiency
AwarenessGreat282@reddit
Really? Never seen one? Very common starting in the 80's purely for mpg. Jeep, Ford, GM, Hyundai. Performance cars starting using them later but were tuned for max performance not mpg, like Jeep.
kilroy-was-here-2543@reddit
I’ve never been in any manual vehicles from that time period, so that’s probably why I haven’t seen them. And the only manual vehicles I’ve driven were from the 60s
perfectly_ballanced@reddit
That's not necessarily the case, even if you're allowed to drive at 30 mph, you'll end up being in a lower gear, which would be significantly less efficient
AwarenessGreat282@reddit
lol, sorry, I didn't think anyone would take it to the ridiculous low speeds regardless of legality. I was thinking 55mph as the lower limit for most highways.
Humble_Handler93@reddit (OP)
Haha unfortunately 😅
todd_i@reddit
Back in the 80s and 90s the US had 55MPH national speed limit and drive lines were getting computers. Most American vehicles had most of their tuning efforts at 55 and got the best mileage at that speed. The national speed limit as been repealed(not sure when). I am not sure what speed they are tuned for now. The EPA mileage rating is very important and they are for sure tuned to get the best score possible on that test circuit.
bluedream71@reddit
Drive with the flow of traffic and don’t be the ass hat braking all the time looking at your “Econo meter” just to save half gallon of fuel.
Robobeep-@reddit
The slower you drive the better your efficiency. It's aerodynamics. Think about how an airplane takes off, it actually uses that drag to float on air. That drag is pounding your vehicle more the faster you go.
You just don't realize the efficiency when below highway speed because of the stop and go, mainly the fuel that gets consumed to get going again.
MrMeesesPieces@reddit
69
Life-ByDesign@reddit
89-96 km/h
ChemistAdventurous84@reddit
I believe that wind resistance goes up as the square of the velocity. At least that’s how I remember Click and Clack explaining it. I’n too lazy yo verify that tonight.
aloofman75@reddit
In general, it’s a low RPM in the highest gear. Whatever that speed is will be the most fuel-efficient speed, but that will vary depending on the vehicle, road conditions, etc.
It’s worth pointing out that it’s only in the most optimum conditions that you can drive your car that way for an extended period of time. In the highest gear, your car probably doesn’t have much extra acceleration to tap into. And stoplights, traffic, etc., will prevent you from driving that way very often. And depending on the situation, arriving at your destination later might cost you more money in the long run.
ChloricSquash@reddit
Are there semi trucks on this trip. Right behind doing their speed is the best answer. Not on cruise. They'll accelerate downhill and reduce speed uphill due to their load. You won't have to think about how to hypermile it will just happen. Try not to run the AC if you can manage, other electrical accessories don't really make an impact.
JCDU@reddit
Worth saying Mythbusters tested this and found that drafting behind trucks doesn't save you anything significant unless you're about 6" off the back bumper.
Driving slow & steady at a safe distance behind the truck will improve tour MPG just because they keep it steady and don't brake or accelerate hard if they can avoid it, but do keep a respectable distance.
ChloricSquash@reddit
Completely wrong. Also the vehicle tested matters significantly, aero has changed a lot since mythbusters, you can feel yourself lift when you catch the draft at 70mph, and you don't have to get nearly as close as you think.
JCDU@reddit
Someone else posted the results and yeah they did save some gas but worth saying they started at 100' out and got very close to see significant savings - the safe stopping distance being closer to 200' at 50-60mph.
And pissing off truckers is not a good plan either.
ChloricSquash@reddit
Stopping distance is much worse for a truck. I guess to each their own.
JCDU@reddit
That's car stopping distances.
ChloricSquash@reddit
So does the truck warp to another universe or require more stopping distance? Both of you have to stop.
JCDU@reddit
If the truck stops and you're not paying attention, you hit the truck. You can't see through the truck.
ChloricSquash@reddit
If you're not paying attention you shouldn't drive?
JCDU@reddit
You and I both know that would remove about >50% of people from the roads if it was enforceable.
ChloricSquash@reddit
1000%
Gutter_Snoop@reddit
Depends on the vehicle too. An already aerodynamic car isn't going to benefit as much as a boxy chonker. Also, around one trailer length the air becomes turbulent, and that's about where benefits begin to deteriorate no matter what you're driving. Lower-profile cars can still benefit some but taller vehicles start losing any gains.
radonfactory@reddit
Still unsafe tho, OP would be better off just building an air dam out of acrylic or something
Gutter_Snoop@reddit
Mythbusters also didn't do it well. They claimed it was the "constant throttle feathering" that killed econ savings. If you're not a clod on the pedal, you'll do fine. Also, it's was a nationally aired TV show. Did you really expect them to say "yes it works wonderfully! By all means you should draft semis!" They'd have gotten soooooo much hate mail.
Anyways. You get the best savings within a trailer length. I used to do it all the time and saw decent savings.. going from like 30mpg to like 35mpg. Now I'm older and wiser and realize the pittance of savings isn't actually worth the trouble. Or potential accident.
outline8668@reddit
A trailer length is 50' which sounds right in line with the mythbusters results. But like you say who wants to be that close. Around here you'll get the front of your car sandblasted by being that close.
Gutter_Snoop@reddit
That's just basic aerodynamics. At around 100kph, your best benefits are within a vehicle length on pretty much any vehicle. It scales pretty linearly too, such that at 200kph, it'll be about two vehicle lengths.
ChloricSquash@reddit
So what's the distance on a semi? That doesn't qualify at all close to similar length.
Gutter_Snoop@reddit
I'm...... really not sure what you're asking. You get the most draft benefits up to one trailer length if you're in a car. If you're in a taller vehicle like an SUV or RV, it's a little closer, since the turbulent are coming over the top tends to start dipping closer to the road after about half a vehicle length.
This gif demonstrates what I mean. You can see how the air swirls off the back. Blue is air moving at about the same velocity as the truck. The green is air that moving along with the truck, but not as fast. Orange is ambient air (presumably stationary). As you get to almost a trailer length, there is more stationary air mixed in with the "green" air. That's the turbulence zone where your aerodynamic benefits while drafting start to rapidly fall off.
ChloricSquash@reddit
2 trailer features the image doesn't apply as well to, drop deck trailers and the skirts they place on trailers now. My only point is 53ft is a long way imo and you can feel the benefits pretty quickly.
Maybe I didn't understand if you thought it was a good or bad idea lol
Gutter_Snoop@reddit
Well, I am saying when it comes down to it, in most circumstances drafting isn't worth it to me. Let's evaluate:
I have a car that gets 30mpg just fine. Say I draft a semi for an hour on my commute of 60 miles each way. At best I get about a 15% increase in mpg, so say 36 mpg. At the end of the day, I save about half a gallon. Gas here is around $4/gal, so I save $2. That is absolutely not worth my time, especially if I'm having to follow a semi going 10 under the speed limit.
The shorter the commute, the less you benefit. The less time you're actually behind a semi, the less you benefit. You start erasing benefit if you have to brake or accelerate at all to stay in the wind shadow. If you get a ticket for unsafe following, that erases years of presumed benefits. If you get in a fender bender, you'll probably never actually recoup the loss. Point is, when you evaluate risk/reward vs actual gains, drafting just isn't worth it in 99% of circumstances.
ChloricSquash@reddit
Saved 1/3 of a gallon but I digress.
I won't follow a semi doing less than the speed limit. On a long drive is the only time I'm interested, you have to do some math but in my vehicle it cuts out a gas stop from Louisville to the Florida panhandle thus saving time to arrive at the destination.
JeffonFIRE@reddit
I remember quite the opposite. There was some fairly significant savings, until you tried to maintain a distance that was TOO close. Then, the constant throttle corrections to maintain the distance lowered fuel economy
I ran down the full episode: https://youtu.be/VabClSuOi_8?feature=shared&t=1867
The basic data shows:
control: 32mpg
drafting @ 100': 35.5mpg (+11% improvement)
50': 38.5mpg (+20%)
20': 40.5mpg (+27%)
10': 44.5mpg (+39%) <---- highest
2': 41mpg (+28%) <---- falls off
JCDU@reddit
I misremembered that one then - worth noting the safe stopping distance at 50mph is 175ft according to the highway code and following closer is going to wind up the trucker and look very bad in the accident report.
Coffee_Grains@reddit
For what it's worth, most if not all modern passenger cars will stop in a shorter distance than a semi.
JCDU@reddit
That's car stopping distances - and yes many can stop a lot faster than the highway code suggests but that assumes the driver is paying attention.
ChloricSquash@reddit
Speed matters too, extending the tail and increasing the value gain on vehicles with a higher drag coefficient.
Odd_Language6495@reddit
This phenomenon is extremely noticeably on a motorcycle. If you get close enough it feels like you could turn the bike off and it still just pull you.
ChloricSquash@reddit
How close do you have to get? People keep screaming about safety, while they're not wrong. I've never felt unsafe with my distance when the draft kicked in.
Odd_Language6495@reddit
Stupid close. You can't see around the truck at all. You can feel the draft on a motorcycle further back, but it kinda knocks you side to side a bunch. If you get even closer, that goes away. But I would say you are 1 or 2 feet off the bumper at that point.
ChloricSquash@reddit
In a car this isn't my goal. I can gain a couple mpgs at about 2/3car lengths that's all I can handle lol. I gain even more by not driving aggressively too.
Odd_Language6495@reddit
I was thinking you could have a grappling hook you throw onto the bumper of the truck.
BookFew9009@reddit
But don’t get butt hurt if the trucker brake checks you . Drafting will obscure you from his line of vision in his mirrors , affect his fuel economy and is basically tailgating for you to achieve any real efficiency.
ChloricSquash@reddit
If you get close enough they never see you then why brake check? 🤣
You don't have to get as close as you think. Just close enough you feel yourself lift to keep up speed.
Otiskuhn11@reddit
Drafting a truck actually improves its fuel economy, but they still don’t like it.
5141121@reddit
Just remember that time is also not free. There's a third vector in the efficiency equation.
Whether or not it's significant enough to make a difference is something only you can determine.
In my '05 TDI Beetle, I could average 50MPG (550 miles/tank) if I kept it at about 65, which was generally fine if I stuck to the right lane. The difference in time with following traffic (in MI, it's typically 75-80) ended up about 15 minutes on my commute, which was far outweighed by the fuel savings (about 60-100 miles/tank).
samocamo123@reddit
To be fair a 15 minute difference between 65 and 80 requires a commute of over 86 miles, so time is likely to be a relatively small factor for most people
PaulClarkLoadletter@reddit
And also, nobody is making up 15 minutes on an hour long commute by speeding unless the entire commute is free of traffic and lights.
toyeetornotoyeet69@reddit
If you're like me, and drive on 80% interstate, it adds up. Especially if you beat traffic by leaving a little early and also driving fast in the safe parts
PaulClarkLoadletter@reddit
Distance is what makes it worth it unless you get tickets all the time or your car chugs over 75mph.
Errenfaxy@reddit
I realized this truth one day driving an hour to work when I was late. It's just not worth speeding and increasing the chance of an accident to try and make up a little bit of time. I slowed down, was 10 mins late, and nobody noticed.
PaulClarkLoadletter@reddit
I stubbornly gave up after hauling ass and weaving to “make up time” while a slow, old woman in a white Camry caught up with me at every goddamned light. It’s just not worth it.
2003RedToyotaTacoma@reddit
I make up 30 minutes on my 2 hour round trip commute by carpooling
see_recursion@reddit
OP said it's open road driving with no traffic. Yeah, stretches of road like that still exist.
5141121@reddit
"Whether or not it's significant enough to make a difference is something only you can determine" is what I said to the OP. So, yeah.
For some, 15 min over 86 miles is enough to be significant if the fuel consumption difference isn't that much. For others, it might not be. 15 min a day can add up over time, particularly if you are already a time-crunched person.
But again, exactly what I said to the OP, they need to make that determination for themselves.
Zachary-BoB@reddit
I’m in agreement, I drive 100 miles a day almost on the dot and manage to get back almost 30 minutes by driving the speed I’m comfortable with vs the posted speed.
Over the course of a year it’s literally almost a week of my life that I get back with my family.
chitown_illini@reddit
OP did say he was going 200 miles per day.
typi_314@reddit
My commute is 600 miles a week. 60mph = 10hrs, 65mph = 9.25. So for an entire week I save 45min by going 5mph over.
wastedpixls@reddit
This is also something that needs to be a common calculation element with work. If you have to drive an hour each way to/from work it takes you 10 hours to do 8 hours of work so you need to dilute your hourly average by this amount, and THEN add the cost of travel in fuel and wear factors.
An example of this is if you're driving an hour each way for a $30/hr job, when you add your travel time it bumps it down to $24/hr before travel expenses.
Rocket_Monkey_302@reddit
I negotiated a higher starting wage because I demonstrated with real travel times and calculated fuel mileage from my commute to the interview, that the offered wage was a financially poor choice and I could not accept it.
An 8 hour shift took 9.5 hours with almost no traffic and consumed 2 gallons of fuel at around 30 mpg IIRC.
Good faith argument. I cannot change jobs to have less real money or a lower actual rate. Your selling your time ultimately. It's not their problem that I'm driving 1.5 hours or using two gallons of fuel, but I can build more wealth at two bucks less around the corner from my house. I already got a job, make me an offer I don't need to turn down.
jabeith@reddit
I'm from Canada guy I was traveling through Michigan last week. The speed limit of my side of the border is generally 90kmph (55mph). Driving through Michigan where the highways are all basically 75mph I was driving 80 to go with the flow of traffic. My car has an indicator that's green when you're driving fuel efficiently and white when you're not. Didn't see a lot of green those days, but at least it felt like I was making good time.
By the way, Michiganers; use your blinkers when changing lanes at 90mph please.
InfluenceRelevant405@reddit
You can't, thats called "warning the enemy"
chefjono@reddit
I've noticed that when driving from Ontario into NY or PA Tons of roadkill, like one deer every few miles.
Maybe its seasonal, or again, maybe highway patrols differ. Sure are a lot of deer in Eastern Ontario.
NickElso579@reddit
Helps when our gas is like 25-50% cheaper
jabeith@reddit
Yeah, it was around $1 CAD / L vs $1.50 CAD where I live
sweetrobna@reddit
Saving 15 minutes is not at all realistic in the real world commuting. Driving faster just means you hit traffic slightly sooner but then you get to your destination at the same time.
Realistic-Ad1498@reddit
At 200 miles of driving, shaving off 15 minutes is easy. Going 55 will take over 3.5 hours. Doing 80 will take 2.5 hours. I’ve done both speeds for long distances under different circumstances.
I’ve never had a vehicle where the money saved by driving more efficiently was worth more than the time saved driving as fast as possible within reason.
Zattack69@reddit
I can second this that for a roadtrip I took in my 2011 VW gold TDI I averaged around 50 MPG if I just took it nice and easy, hovered around 60/65 MPH and just kept in the middle or right lane (depending on traffic). I liked being able to not see the fuel gauge plummet rapidly 😂
belinck@reddit
In MI, it's typically 75-80, except for when you're on the Lodge which is 85-90 ;)
Gutter_Snoop@reddit
96 minimum on 96!
Otiskuhn11@reddit
85-90 while getting shot at*
Zociety_@reddit
I like this take too.
Known_Lead_5320@reddit
2k rpm
balanced_crazy@reddit
When my pilot is loaded with people 55 and 35 are the most fuel efficient speeds.. When it’s just two of us, 45 and 80…
Wolf_Ape@reddit
Cruise control is rarely ideal for efficiency. Most I’ve experienced seem to punch the gas on slight hills or against headwinds. It depends on your gearing. 1500 rpm’s at 50mph is less efficient than 1700rpms at 85mph, but you’ll have time to find the best trade off between keeping speed up and rpm’s down
Wassup4836@reddit
55-60. After 65 you lose a lot of fuel economy, it’s the worst at 67.
H0SS_AGAINST@reddit
Depends on the efficiency curve of the engine. Assuming you do not have a performance or turbo engine, the lowest speed in top gear that doesn't lug. If you have an engine designed for volumetric efficiency at higher RPM, then it will be finding a balance between RPM and drag in top gear. If you have a turbo engine, you will probably see the best efficiency at the RPM in top gear that just barely gets into the turbo recovering energy from the exhaust.
The thing is, 200 miles is a lot of time. Personally, I am not turning a 3hr drive into a 4hr drive to save a couple gallons of fuel. Say 20mpg at 70 and 30mpg at 50. You'd save 3.33gal or like $12-15. If you have a more efficient vehicle the fuel savings are even less. Say 30mpg at 70 and 45mpg at 50, you'd save 2.22 gal or $6-9...for an hour...so minimum wage.
Nicadelphia@reddit
Not sure where but I did read once that your fuel economy starts to reduce around 65. It's also the speed that your bad alignment ghosts come out.
Mybadbb@reddit
The general consensus is that 55-60 is the most efficient speed, but it can vary slightly depending on the aerodynamics and gearing of the car. I usually set my cruise control to 60 and stay in the right lane when I drive my 1996 Jeep Grand Cherokee and I manage to get 20-22 mpg, which is impressive considering it's rated for only 17 highway and it's an almost 30 year old V8 SUV with well over 200k miles and the engine light is on, lol.
cty_hntr@reddit
The original 55 MPH speed limit was imposed during the oil crisis in the early 70's. As you stated, it's the efficiency sweet spot.
fearsyth@reddit
Cars also had more drag, less efficient engines, and less gears at the time.
Now, some cars will run most efficiently at speeds up to 65mph.
NockedSenseless@reddit
This is true with my 2016 mustang gt. It gets 27mpg at 65 on flat ground, and at 73mph I get 30.1. gotta drive this thirsty ass car like a grandma, because in town I get 11mpg.
Iggyhopper@reddit
My car can go 80 and it reads 32 miles per gallon on its sensors. Very impressive for a 2018 SUV
InfluenceRelevant405@reddit
Its sensors are stroking you, fill up and record miles, drive til fuel is low and do math. You will see that it lies to you
Mybadbb@reddit
Eh, maybe not. It depends what their "SUV" is. If it's something like an Escape, it's pretty much just a lifted Focus. Something like an Expedition or Suburban claiming 32 would raise some suspicion though...
InfluenceRelevant405@reddit
I was driving a kia soul, over the course of a month the onboard was claiming 40+ mpg, I did the math and it was more like 35, very good for a month of driving but the computer was still way off
No_Candidate_3676@reddit
I had a 96 GMC Sierra that would average almost 28 with a 5.7 V8 and 4*4. And at 17-18 years old I wasn't exactly nice to it lol
KeyboardJustice@reddit
With electrics, it's better efficiency most of the way down in speed, so if there's an island of efficiency at higher speed, then it's likely due to an inefficiency in the gearing ratio.
Aggravating-Arm-175@reddit
It's inefficiency in the valve timings, that is why most modern engines have newer valve timings systems
gstringstrangler@reddit
Drag is exponential tho, it's the defining factor in fact. Not that what you're saying is incorrect, but finding the sweet spot for any vehicle is largely governed by drag and where the powerplant makes the most efficient use of...power.
Allow myself to introduce... Myself
KeyboardJustice@reddit
This was my point! You'll notice I said ev follow this trend, so when a gas seemingly doesn't it's gonna be some other big inefficiency at those reduced speeds that negates the drag gains.
gstringstrangler@reddit
I think I was just adding the reason you left out lol
fearsyth@reddit
Yeah, with EVs you're not wasting a lot of your energy every second. EVs are probably going to get the best efficiency around 20 mph.
Gas engines waste enough that you need more speed to make up for the wasted energy.
rklug1521@reddit
Some Corvettes can get good gas mileage at 80mph.
Vedfolnir5@reddit
Tires as well. Tire technology has come a long way
Boot_Shrew@reddit
Oh yeah? Tell that to my cross ply tires skids off into the distance
PoetryBeneficial6447@reddit
You mixed with radials didn't you?!
Boot_Shrew@reddit
I mean they were retreaded radials so surely they're good. Right?
TerpsR4theKids@reddit
Well they wouldn’t retread a bad tire now would they
Boot_Shrew@reddit
I couldn't tell the sidewalls were are wiry or something
deverox@reddit
I5 at 90 massacres my mileage…
Opposite-Knee-2798@reddit
Source? The ideal speed for efficiency could have been lower but it might have been impractical.
ChimneyNerd@reddit
Yeah definitely depends when your car was made too. I have an ‘86 Honda Prelude and it was made when the highway speed limit was 55, so going 60 makes it lean a bit higher in the rev range and become less fuel efficient in top gear nowadays.
belinck@reddit
I've had 4 Jeep Cherokees and 3 Grand Cherokees over the years. I'm pretty sure the check engine light is on from the factory.
SyntheticOne@reddit
You can order the dealer installed "Negation of Check Engine Light Device" which is a $25.00 (installed) piece of black electrical tape. For another $100 they will throw in a tire rotation.
Independent-Owl2782@reddit
Oh that is is good. LOL . Loving it. I'm sure that is done in lots of garages. I know someone who use to take the bulbs out.
Shroomboy79@reddit
Or you could just be a real man and cut the wire somehwere along the way so no future owners will ever have a check engine light again without replacing the entire wiring harness
Independent-Owl2782@reddit
That would be way easier.
Shroomboy79@reddit
Apparently whoever owned my car before me thought it would be
belinck@reddit
I read that in Tom Mariozzi's voice.
SyntheticOne@reddit
Click and Clack to the rescue!
Mybadbb@reddit
It's a Jeep thing I guess...
I've got a quick question for you, maybe you'll have an answer since you've owned so many. Recently, maybe half the times I start the Jeep up it'll die immediately after firing up. It's more likely to happen when the engine is cold but it's happened on a warm engine too. I can keep it running if I immediately rev it up to 1500rpms (wouldn't dare go any higher when it's ice cold) and hold it there for a minute or so, and once I drive it down the road even a little bit (like to the stop sign half a mile down the street from my house) it'll be fine and doesn't shut off at all. Any ideas?
gstringstrangler@reddit
Fuel pump
Oh wait I should ask what Jeep... What Jeep?
Mybadbb@reddit
1996 Grand Cherokee 5.2, bought it early this year and the previous owner said the fuel pump had just been replaced.
gstringstrangler@reddit
Ah ok, 4.0XJs do what you're describing and it's the fuel pump but I can't say for sure on that one. Honestly, search Jeep forum, every remotely recurring issue ever has a fix where factory or and upgrade etc.
belinck@reddit
When was the last time you changed your plugs and distributor?
Mybadbb@reddit
I haven't changed them at all, bought it about 6 months ago. I changed the air filter and serpentine belt only so far.
223454@reddit
Can confirm. It's always mad about something.
Maleficent-Ad2359@reddit
Thought it was a chevy thing only, 2, 2006 pickups, and an 02 astrovan, been on since I bought em...
TheSnackWhisperer@reddit
Can confirm, mine just turned back on Friday, if it hadn’t I was worried I’d have to take it to a shop.
Mybadbb@reddit
So true, mine had been lit up for a long time until a few weeks ago it randomly turned off and I legitimately got worried that something was actually wrong with it now, but it comes on intermittently now.
xtnh@reddit
A great way to simulate dragging a brick through water.
Aggravating_Kale8248@reddit
I had a 2014 corolla that would get 42-45 mpg at 60MPH in the summer on the highway. That thing was stupidly efficient for its size.
halfcocked1@reddit
We had a '87 Corolla that would do the same. With Corolla's around, I wondered why anyone would by a Smart car since they don't do much better for how much smaller they are.
Aggravating_Kale8248@reddit
Smart cars have price on their side. They are cheaper than a Toyota, so that’s the draw for many.
Jond0331@reddit
Holy crap, that's amazing!
Opposite-Knee-2798@reddit
Source?
Ammar_aamir20@reddit
Reading this made me imagine you saying this all really fast and in one breath😂 Good information tho
iamr3d88@reddit
Thank you.
I don't care how fast or slow anyone drives as long as they aren't blocking traffic. Now if you are doing 60 next to someone else doing 60 in a 70, someone's gotta speed up or slow down.
Albert14Pounds@reddit
Don't sleep on 50 though if you have an non- aerodynamic vehicle though. I seem to get better mpg at 50 if traffic allows it.
AnastasiusDicorus@reddit
Don't think you have to go that far. I had an old suburban with a 350 that got around 22mpg at 58-60 but dropped down to 15-16 mpg at 65-70.
Humble_Handler93@reddit (OP)
I’m in no rush so 55-60 isn’t too bad. My Avalon’s light is on too but it’s from a faulty connector for an o2 sensor
right415@reddit
If it's an upstream O2 sensor, it will dramatically affect your fuel economy. If it is downstream (post catalyst) it doesn't affect fuel economy at all.
NicknameKenny@reddit
Get that O2 sensor fixed and experiment with your actual personal vehicle. Compare the average of multiple runs at different speeds and report back here. (It'll likely be around 62 mph)
IHuffFartsFromJars@reddit
Dude what my 2021 grand Cherokee gets like 16 mpg
queefymacncheese@reddit
Check engine could be on duentonit running lean which would also explain the gas mileage.
yottyboy@reddit
This is usually due to oxygen sensor failure. Get new from rock auto and a o2 sensor socket from amazon. You should see the light go out
ChopCow420@reddit
My 2003 dodge grand caravan which is literally falling apart is 250k miles and gets 21 mpg I do not understand but I appreciate.
adultdaycare81@reddit
I’m shocked you aren’t run off the road going that slow.
Mybadbb@reddit
The speed limit on my local 2-lane highway (non interstate) is 55. I don't always go 60, sometimes I go 65 or even 70 if I'm really in a hurry but old Jeeps don't really like that, lol. It's weird, there's times where going 60 I find myself passing people while other times going 65 there's people riding my ass and cutting me off to pass the person on the left so they can go 85 instead of 80. Time of day is pretty irrelevant to this too.
Electronic-Youth-286@reddit
Some manufacturers game EPA testing by leaning out the air-fuel mixture at engine speeds that correlate to 60 MPH. As a result, you can have an efficiency "notch" at that speed that you might not get at speeds 5 MPH lower or higher.
Dredgeon@reddit
Yep, cruise control on backroads goes me upwards of 40 mag in my Jetta (it was 50 before my wider performance tires.
TruthImpressive7253@reddit
Put tape over the warning lights
Kurtman68@reddit
Do not use your cruise. Gently accelerate and anticipate traffic. Avoid the brakes whenever safe to do so. Accelerate slightly going downhill and allow the car to slow when ascending hills. If you have a fuel economy display, keep an eye on it and use a feather touch on the accelerator. Once you’re at highway speed, back off the accelerator until you’re right on the edge of just maintaining speed but not slowing down. This is your most efficient road speed. I recently did a cross state trip like this and increased my avg fuel economy from 26 to 36mpg. 2016 2.5L Outback.
Interesting_Pilot595@reddit
whatever it takes to get into 4th gear on the avalon
Beginning_Lifeguard7@reddit
Slower is better. The best mileage I’ve ever gotten was driving at all day in a national park at 35 mph. You don’t mind your commute taking 6 hours a day do you lol. Figure out how long you’re willing to take on the commute and then drive that speed.
MarkVII88@reddit
Air resistance increases exponentially the faster you go. Big difference in air resistance going from 60 to 70 MPH. Much bigger difference going from 70 to 80 MPH.
It's going to be a trade-off between fuel economy, time spent driving, and stress related to other drivers blasting past you or tailgating you, if driving at 60-65 MPH on the highway. Personally, I wouldn't drive below 65 MPH, and would probably end up splitting the difference between speed, time, and economy by setting my cruise to 70 MPH. I usually set my cruise between 72-75 MPH, depending on how fast the traffic is going.
Accordingly_Onion69@reddit
55ish get my civic si rated at 31 mpg get a conservative 47mpg
Lance_Notstrong@reddit
I think it depends on the car. I drove from SC to OK and back. My 911 gets better gas mileage at 90-95mph than it does at 65mph….and by a large margin. At 65mph, I was able to get 366 miles on a tank of gas. At 90mph I was able to get 399 miles. Have done this drive a few times and the results are the same and repeatable. In my Cayenne and Macan Turbo though, go faster than 75mph and the gas mileage plummets.
Ferowin@reddit
I track mygas mileage relentlessly and can safely say there isn’t one speed that’s best for fuel efficiency, though I typically do the best at about 55 to 60. At 65 it starts to drop a lot and at 75 it is positively abysmal.
Fuel efficiency depends on a lot of things including weather (temperature, humidity, and air pressure), the condition of your vehicle, and your driving style.
The easiest things you can do to improve your mileage are to make sure your tire pressure is correct according to the label on the drivers door sill, remove unnecessary heavy items from your vehicle, set a good speed on your cruise control and maintain it, and don’t take off or stop suddenly.
Things that most hurt fuel mileage include low tire pressure, sitting at red lights, driving excessively fast, and changing speed unnecessarily.
Sparky62075@reddit
Every car is different and every road is different. Use a different speed each of the first five days varied by a few MPH. Start the drive with a full tank, and then fill up at the end of the day. Whichever speed needs the least fuel is your winner.
BLDLED@reddit
Not necessarily. In an area that gets strong varying winds, it can have a significant impact on MPG. One area near me can have 40mpg winds in either direction. So one day you go 60mph, but have a 40mph head wind, then the next day you go 70mph but have a 40mph tail wind. The 70mph day Weill be better mpg, with an 80mph delta of wind resistance felt by the vehicle.
Conwaysp@reddit
Generally wherever your car changes into its highest gear becomes the point where you're moving the fastest with the lowest RPMs.
For most vehicles though this won't be a satisfactory highway speed, and might even be below the minimum so as to be potentially dangerous.
I think the show Top Gear (original UK version) did a piece on this and hypermiled a car by running a full tank to empty on a highway trying to reach a specific destination, and traveled over 1100kms/680 miles but were only doing just over 70 kms/hr or 45 miles/hr.
PowerfulFunny5@reddit
I have noticed that really long stretches of road construction where you are stuck going 45-50 mph seem to be more fuel efficient than 55+
VascularMonkey@reddit
Same, I get significantly better mileage on small highways where actual driving speeds are more like 45 - 55. And that's after losing all the energy from more stops, starts, and speed changes.
Conwaysp@reddit
Only if you keep moving though. It's the slowing/stops and starts that cost the most in fuel economy, but you know...safety.
another_mccoy@reddit
Yeah, my fuel mileage goes WAY down when I have to push the cars in front of me... /s
PowerfulFunny5@reddit
Yes, I was thinking about 10+ mile construction zones where you don’t stop.
Zippytiewassabi@reddit
This, the faster you go the more air resistance becomes a factor. I’ve saved fuel by cruising as soon as I hit my last gear and trying to maintain that. Usually 40-45. However I like to have a little potential energy with a faster speed like 50-55 so if an uphill is coming I can keep the throttle position and gear even if gravity decelerates me down to 40-45.
mcnabb100@reddit
Absolutely right. I can shift to 6th in my civic by about 45mph or so assuming there are no steep hills. The only thing that going faster will accomplish is creating a greater amount of drag
InfluenceRelevant405@reddit
It was in an audi a8 tdi. He kept the rpms as constant as possible at around 1800. Cruise control wasnt used at all because the revs climb when on an incline
Waveofspring@reddit
Not necessary in modern cars with gas mileage calculators
KitchenPalentologist@reddit
Also.. wind can be different. The difference between a 20 mph headwind and 20 mph tailwind is major (40 mph combined), and will affect the most fuel efficient speed for a given car.
OPs Avalon should have a fuel computer, no? Something that gives instant and overall MPGs? It seems pretty easy to do some testing.
Sparky62075@reddit
The vehicle is 22 years old. It may not have anything like that.
Otiskuhn11@reddit
Outside temperature, wind, and precipitation will change everything.
netopiax@reddit
Even then you'd need to correct for hills
No-Explanation1034@reddit
If its the same route and mileage that would be irrelevant.
netopiax@reddit
Somehow I had road trip in my mind instead of commute... you are right obviously
IllMasterpiece5610@reddit
Assuming you’re not changing your speed very often (because acceleration uses most of the fuel), wind resistance is going to be the biggest factor.
I might not remember this right (it’s been 4 decades since I did this sort of thing), but at low speed, wind resistance can basically be thought of as increasing linearly with speed, but once you reach Mach 0.1 wind resistance increases proportionally to the square of speed. Mach 0.1 is around 110km/h (or 68mph) at sea-level and 20 degrees Celsius.
So keep it below that speed and try to avoid accelerating (keep the speed as constant as possible and accelerate before the road goes uphill).
I averaged 4.5 litres/100km when I moved 4,500 km away with all my stuff in a 20 year old car that ran off a carburettor.
Progresschmogress@reddit
Look less at the speed and more at the revs
Assuming it’s an automatic 5 speed transmission with no tip tronic type stuff where you can’t shift manually and therefore can’t choose when to upshift, all you can really do is be super granny like getting up to highway speed and then setting your cruise control when you are in 5th gear and hit 1.3-1.5K rpm as long as it’s not unsafely slow
The lower rhe rpm, the less fuel you’ll burn
Ornography@reddit
Lowest speed is most fuel efficient. But since you’re on the highway, get to the highest gear(overdrive) and get to the lowest rpm on that gear
Suit_Responsible@reddit
Pretty sure they most effect speed is going to be around 45-50 for most cars…. But don’t do that on most big road. Go a little faster
Xhebalanque@reddit
The most efficient speed will be the speed you have to adjust your speed the least.
Maintaining your speed isnt needing that much energy, well there is air resistance.
Far more energy you will need accellerating and braking.
So most efficient speed is most likely going to be 90-110 km/h depending what speed lorries are going in your country and what is enforced.
Also windshadow riding will help there
Upbeat_Experience403@reddit
I would say it depends on the vehicle and the gear ratio I have one truck that does the best at 55 and I have another that does the best at 70.
chumlySparkFire@reddit
Traffic never allows this, but the max MPG is about 40MPH in top gear…. My 2020 Accord at 55MPH gets 42MPG on pump gas…. Honda knows more about piston gas engines than anyone else on earth, obviously. As the largest small gas motor maker, they make 15M engines a year… Briggs and Stratton being the worst gas motor maker on earth.
mackdandy@reddit
What size of engine ?I found keeping my revs just below 2000 was the sweet spot for cruising.
Ok-Rate-3256@reddit
I always just stay behind the semi's. No one rides your ass for going slower that way, and you save on gas.
RunCyckeSki@reddit
It is a balance between engine rpm and intake pressure. Minimizing both will result in the best fuel economy. In my experience this is usually around 50 mph, but that is too slow for most freeways. So basically, as slow as you feel comfortable going on the freeway.
If you really want to get scientific, I would suggest installing a boost/vacuum gauge on your intake manifold. I have these on all of my vehicles. This tells you the intake pressure and is very indicative of fuel economy.
ChrsRobes@reddit
Times not a factor? The ideal speed is around 45 mph. It's dangerous to go that slowly on the highway however.
PeddlerDavid@reddit
The slowest you can go in top gear, Around 35-40mph in many vehicles.
Ponklemoose@reddit
IIRC: Aerodynamic drag starts to matter at about 35 MPH, so that is probably your sweet spot.
That’s probably too slow, but closer will be better and the real question is how you value your time vs money.
jassoon76@reddit
I drive a 2016 Chevy colorado and constantly get between 25 and 35 mpg on the highway. I set the cruise at 65 and turn the ac off, and keep the windows up. If I can stay behind a bigger vehicle, I will. Now, saying this, u have to keep pace with traffic and not cause issues with the flow. Prime example I-75 between Saginaw and Detroit is a minimum of 80 or u are in the way.
SunyataHappens@reddit
55 mph. That’s why it was set at that in the 70s during the OPEC oil crisis
ethos1234567890@reddit
I’ve always wondered this as well and thought that it should be the speed at which you’re in top gear and rpm’s are stable at the torque peak for your engine. Is that not correct?
wheelsnbars@reddit
Within the first week you will be able to find this out for yourself.
Cruise control isn’t the most efficient way to drive anyway, consider the hills, speeding up on the way down etc…. As well as headwinds and drafting other vehicles.
One-Butterscotch4332@reddit
My a4 is most efficient at like 45, it hangs out at 1k rpm there. It starts to fall off above 65.
SwissMargiela@reddit
Whatever speed is the lowest rpm you can drive at your top gear
Waveofspring@reddit
This depends on the car, whatever speed has the RPM gauge needle at the lowest point.
My car has 8 gears, in the last gear, after 60-65 the needle starts going up, meaning my engine is spinning at higher RPMs and thus using more fuel.
So for me 60-65 (I think 65 to be exact but I’m going off memory)
AlistairBarclay@reddit
Surely all you do is look up the torque curve for your vehicle, note the rpm it’s achieved at and drive to that rpm once rolling.?
Gavolak@reddit
What car and what year is it? Best MPG will depend from car to car, but the main factors to consider are your engine and the type of fuel. Generally, the highest gear and lowest rpm will give you the best gas mileage for any car. This is ideal for highway cruising. Since you’re going 200 miles, aerodynamics will matter too but to a much lesser degree than your engine configuration. The best way to improve aerodynamics in any car is to simply keep all your windows closed. Any opening where air can come inside the car will create a lot of drag, so just avoid that and use ac.
DangerMouse111111@reddit
The slowest you can go without holding up the traffic.
SpeedyHAM79@reddit
I'd bet for your car the sweet spot is 60-65 mph for maximum mpg. The trade off is your time and the local speed limits. I wouldn't exceed the speed limit as any speeding ticket would cancel out any savings in time or fuel. If the speed limit is 65, I'd go 65. Might get 0.05 less mpg compared to 60mph- but for 200 miles it saves enough time to be worth it to me.
HunterDHunter@reddit
All day everyday the answer is slower. If you want fuel efficiency, drive slower. These other people talking about it varies from car to car, it doesn't. Go slower, get better mileage. To really maximize, keep the windows up, accessories off, and draft behind a large truck.
heneryDoDS2@reddit
Air resistance is exponentially related to speed. So that means that the difference in drag on your vehicle between 65-70mph is much much bigger than the difference between 55-60mph. So when you get up there in speed you significantly reduce your fuel efficiency with each mph faster your are going. What that means is essentially you should be going about at whatever the speed limit is, as they are generally set around that 60mph range.
Additionally, most vehicles are designed for modern speed limits as well in terms of gearing / efficiency. My truck is a 1ton dually designed for towing @ 60mph, my fuel economy drops like a rock passed 60 because both the air resistance increases AND it starts to drive outside of the speed the gear ratio is designed for. We've got a few roads around me with speed limits of 110km/h (65 mph) and I tend to still keep the truck at 100km/hr (60 mph) because the fuel savings are significant enough vs the small amount of extra driving time I'd need to spend (and it's much much easier on my truck). Plus, all those highways are dual lane so I'm not holding anyone up.
Darkknight145@reddit
I wouldn't worry about fuel efficiency, your main issue will be time spent on the road doing these drives. As you're not doing stop start driving your fuel efficiency will be up anyhow.
Tenos_Jar@reddit
Depends on the vehicle. I've got a '22 Ascent touring and my sweet spot seems to be 65-70mph. My wife's '17 Pathfinder seems to be about the same. Which is interesting given the differences in engines
Fit-Rip-4550@reddit
Depends on a series of conditions, so there is not a standard one.
67valiant@reddit
80-90 kmh depending on the car
badmofoes@reddit
140 you get there faster
spinonesarethebest@reddit
Drive one week at 56mph and the next at 65mph. And the week after at 75mph. Keep a mileage log and let us know.
Ok-Bus1716@reddit
55
LowerSlowerOlder@reddit
Your Avalon has (or at least should have) an instantaneous MPG reading in the center dash display. Start out at 55mph with cruise control on. Once the MPG stabilizes, add 5mph until it goes down. Then back down one MPH. You should close on it pretty quickly.
PrinciplePrior87@reddit
Cruise control 60mph and enjoy the ride, done it weekly runs from NYC to Columbus OH so about 650miles give or take a few and always managed to get close to 500 out the gas tank from the beater honda odyssey i used 2005
RepresentativeAd9572@reddit
55-65 is optimal...many variables wind ,hills, temp etc..but keeping rpm lower is the key
armorabito@reddit
Some where around 2000 rpm in you tallest gear. Usually around 55 mph at others have suggested.
Final-Carpenter-1591@reddit
Almost ways somewhere around 60
alphieboo@reddit
the lowest rpm at the highest gear, whichever speed that gives you is the most optimal MPG
SingleDad37405@reddit
Pump tires 10% harder, do a tune up, filters and oil change if you haven’t, if it’s highway driving … look for a semi truck doing 63, 65 or even 67 and get behind him and stay there, the slipstream works well for MPG.
NewAileron@reddit
Whatever speed the car is at when it is in the highest gear with the lowest RPM.
Signal-Confusion-976@reddit
It really depends on the car and where you drive. My old Honda would average 60 mpg going 75-80 on the highway. That was better than the 50 mpg at around 60. It will also make a difference if you are driving on flat or hilly highways. As far as using cruise control you should measure your gas consumption both with and without using cruise control.
JHZcar@reddit
almost all toyotas are designed and optimized for 55mph as best fuel economy, including my tundra. when i went to 35s the sweet spot became 61mph but those are bigger tires
JHZcar@reddit
acceleration whether speeding up or braking kills your mpg, takes a fuckton of gas to get up to speed, hardly any to stay at that speed
Richyrich619@reddit
35mph but thats not realistic
Manderthal13@reddit
It depends on the car. Each car has a happy place where it just sings along comfortably without much effort. It might be 70mph, it might be 40. Sometimes, it seems that going too slow, the car never finds its rhythm. I'd imagine a 6 cylinder Avalon would be a highway mile muncher.
fuzzylilbunnies@reddit
In my city, the posted speed limit is 65 MPH. I see this sign, along with everyone else on the road, as we crawl along at 25 MPH. I save gas during my 12.5 mile trek. I fill up every two weeks in my 13 gallon tank. No, it does NOT make me happy, but the savings are something, I guess.
Vtown-76@reddit
The relationship between velocity and wind resistance is not liner, it’s exponential. Double speed,wind resistance goes up x4. It starts to become pretty significant at 50 and up. In summary, the slower you go, the better for fuel economy. 55-60 is probably the sweet spot for most cars, but in many areas this can be quite dangerous as you impede traffic. If the speed limit is 65 I wouldn’t go less than 62 or over 67
KitchenPalentologist@reddit
I've done some maxi-mile experiments during long drives to see how far I could stretch a gallon.
I would basically apply \~5% of the throttle or less. That could propel my car 60-65 mph on a flat, 80 mph on a downhill, and as slow as 40 mph going up (I would apply more throttle to move the speed of traffic if there was any traffic).
VW GTI, I normally get low 30s MPG on the highway, and I was able to get it up to 45 MPG over an hours time.
Otiskuhn11@reddit
Finally someone with the correct answer. 35mph would result in exceptional MPG’s, but you could also get rear ended and die in a ball of hellfire.
InfluenceRelevant405@reddit
No, 35mph is not more efficient in a modern car. Gearing is how cars achieve mileage. If a vehicle is in 2nd at 35 mph and 2500 rpms or in 4th doing 65mph at 2500 rpms 65 is more efficient. Its not even close. You need to be in top gear and in the cruising range for your cars engine.
Gutter_Snoop@reddit
Most cars aren't geared for getting best econ at 35 though. My truck won't even shift into top gear that slow. I see my best at 50-55mph depending on wind.
Otiskuhn11@reddit
You’re mistaken if you think the top gear is synonymous with better fuel economy. It’s more about RPM’s.
Heath24Green@reddit
I beg to differ. I will not get better fuel economy at 2k rpm in first gear than I would at 3k rpm in 6th gear. Gearing plays a big role in efficiency.
another_mccoy@reddit
Have you tested this? 😂
Cautious_Implement17@reddit
this is kinda like asking whether someone has personally tested that the lower drag at 35,000 feet vs 5000 ft offsets the slightly longer distance traveled for a jet.
despite being lubricated, combustion engines have significant internal friction from all the low clearance metal-on-metal interfaces as well as pumping losses. in addition to whatever power is needed to do useful work, it takes about 10-20 hp just to keep the engine from slowing itself down at typical cruising rpms.
it's certainly possible that the most efficient speed is not within the rev range of the highest gear (maybe it's in 5th if 6th is super tall). but 1st gear is so much shorter than 6th gear, it would be nearly impossible to return comparable fuel economy.
Heath24Green@reddit
Nah but i personally take it for granted from being around cars my entire life an an egineering degree, but thats not sound argument is it? considering there is usually a thin sliver of speed you can drive at to have a lower gear be more efficient as shown from the first link below.
See last image here
THIS image from here explains for a given rpm a car in 5th gear will travel 4 times the distance of a first gear for the same revolutions of an engine (or amount of times fuel is used. and assuming I am maintaining speed and not accelerating both are using about the same amount of fuel per firing.
* there is and edge case say where your 6th gear has you out at 200mph for whatever reason then yeah, air drag will probably destroy your efficiency as you will be near WOT compared to the first gear barely cracked throttle.
Gutter_Snoop@reddit
In the vast, overwhelming majority of cars and light trucks/SUVs, you will ALWAYS get your best econ in top gear at the lowest speed it will maintain without downshifting constantly. I promise you.
Otiskuhn11@reddit
I agree.
outline8668@reddit
Yep. I had a couple brochures from 1960s Honda mopeds and . motorcycles that showed best rated mpg at like 25mph because bike aerodynamics are trash.
RustyImpactWrench@reddit
There will definitely be a sweet spot and going slower than that will increase your fuel consumption. The reason is because there are lots of parasitic forces that are not speed dependent, like rolling resistance, drivetrain losses, and friction and pumping losses in the engine. That last one is particularly detrimental to efficiency at low speed.
The speed of the sweet spot will vary from vehicle to vehicle. The less aerodynamic it is, the slower the sweet spot, but other factors contribute like gearing. Anecdotally I would say 50-55 for most cars, and 45-50 for most trucks. EVs are much lower.
Salmol1na@reddit
Not a speed but rather It’s lowest rpm in highest gear
InfluenceRelevant405@reddit
1800 to 2200 rpms is the cruising range for most engines, some are a little higher. Keeping your revs in cruising range for max mpg. Try not to let the transmission kick down for small hills and drive as smooth as you can.
cheeseypoofs85@reddit
Depends completely on gear ratio
Shadow_duigh333@reddit
Your car has a display setting that shows the mpg and gas you get in real time. For me it is 75mph which gives me 36mpg for Honda Accord 2017 I4.
Sea_Researcher7410@reddit
Depends on what you're driving. My old truck, 55 is best, but if I put an overdrive in it, I could bump it up to 65 or 70
Extension_Ad4962@reddit
If your car has cruise control use it. You will be surprised how much your mileage improves if your not using the throttle like an on/off switch.
Kickstand8604@reddit
Your most efficient speed is also dependant upon engine rpm. If you're running a 6 cyl at 60mlh, your rpm should be at or below 1.5k rpm
Great-watts@reddit
Anything below 80 will last about a week at least in CA
July_is_cool@reddit
Around 30 MPH but you will get rear-ended
GearheadGamer3D@reddit
Basically the slower you go in the highest gear is the most efficient, as long as you don’t go too slow to generate enough power. 1300-1700rpm, depending on how much power the motor generates. A big V8 being able to have lower RPM while making sufficient power compared to a small engine needing higher RPM. For most cars it will be around 45mph.
NegotiationLow2783@reddit
Watch your Rams. That will tell you where the sweet spot is. Between 2 and 2.5k will be right there.
nips927@reddit
Depends on the car, you want to it to be in it's highest gear for best results. My focus didn't shift to 6th gear til about 60mph, my truck is in 10th at 55mph. you got to play with it and find the sweet spot. My 18 focus was 65-73mph on the interstate and 63mph on the county Rds I averaged 37-39mog consistently. My 2020 Ford ranger 69mph in the interstate and 59 county Rds I average 23-28mpg. The trick is you want to go faster than semi trucks but slower than other traffic. Most companies govern the speed of semis 63-68mph.
newerascout@reddit
I would drive the same stretch of road at various speeds every day on the way home and record the reported mpg. About 40 mph was the best, but outside temperature also had a big effect.
longhairedcountryboy@reddit
The government says 55 or even less. My Honda Civic says 78. It burns a lot more gas at 55 than 78 and tells you about it on the dash board.
showboat21@reddit
Drive 10% above the speed limit, you save time. Drive 10% below, you save gas. Of course, all of these are relatively arbitrary. Just drive safely!
YogurtclosetNo3927@reddit
The 55 mph speed limit wasn’t because 55 is the most optimal, it was because it was a lot better than 65 or 75. I had a truck once that had a fuel efficiency chart in it, with best mpg at 45 mph.
Basically, the slower you go the better the mileage, but you can’t go 45 on the highway.
I’d drive the first day as slow as you’re willing to go, then calculate the mileage. Next day go 5mph faster and see the difference. Maybe calculate mileage halfway so you can get more data points quicker. Pretty soon you’ll find the optimal speed for your personal situation.
HawaiianSteak@reddit
Did crash survivability factor into the 55mph speed limit?
YogurtclosetNo3927@reddit
My understanding is that it was based fully on trying to reduce the nations oil consumption.
Spksnppr@reddit
The lowest speed that your car drive while in overdrive. In a manual, it will be very slow. In my automatics it’s around 45 mph. My 2008 F150 gets 13.5 at 70. It gets 27 at 45 in OD. My manual Dodge diesel gets over 30 at 20 mph. But 45 and 20 is too damn slow.
PracticalConjecture@reddit
Generally, slower is better for fuel economy. However, your time is worth money, so it may not be worth driving at the most economical speed.
Stop and go traffic is what makes city driving so much less efficient on ICE vehicles, but on the open road where there is little to no braking and fighting aerodynamic drag is the biggest energy consumer, it pays to go slower. Aerodynamic drag increases 4x as speed doubles.
If you go too slow, you start loosing efficiency since the engine needs to burn some fuel to keep itself spinning, and a low speed means that the engine needs to run for longer to go the same difference. with this in mind there's a balance to be achieved.
For most cars, the most efficient speed on a flat road is somewhere between 35 and 45mph. Larger engine vehicles like to go a bit faster since the bigger engine consumes more fuel at idle.
jckipps@reddit
That can vary for different vehicles, mostly based on their overall ratios.
Generally speaking, the bigger boxier vehicles will benefit from being slower. But with some of the sleeker sedans, this is less of a factor.
Have some fun with this. Each tankful, run at a different speed, and see what the numbers actually tell you.
mininorris@reddit
Tire pressure is very important for fuel economy. Higher pressures will improve rolling resistance but unfortunately will increase wear in the center of your tread. Make sure it stays at the intended pressure or a few above to make sure it’s optimized.
ltoed1@reddit
My old 96 accord could do 75 all day at 2.5k rpms, my 06 crv? 3k at 60 lol strictly depends on the car and every one has a sweet spot
The1andonlycano@reddit
Under 2000rpms
Independent-Owl2782@reddit
I think there was a study on that back in the 70s. Not sure though good it was but they casked up with 55 MPH. Given today's more fuel efficient engines my own personal thinking is 60MPH. but there is no science behind that, just my guess. Where I live in Texas we wouldn't get anywhere if we did under 75. But there are so many variables to consider such as type of tires, humidity level, ambient temp., AC use, etc. It can be difficult to give an answer to that. Good question though.
justolazy@reddit
Completely depends on the vehicle and gearing of said vehicle. My truck with a stiff back wind can manage 18mpg at 60mph. My car will get about the same mpg at the same speed, but will get 24mpg-25mpg at 70mph-75mph.
emjdownbad@reddit
I do about the same every work week, and I only fill up once a week w my subaru outback. I also commute in a heavy traffic for about of the commute to and half of the commute from work, but when I have the chance I usually do around 70 mph.
OnlyCommentWhenTipsy@reddit
Usually it's the lowest speed when the car is in it's highest gear. That's a lot slower that hwy speed so just be safe and tailgate an 18 wheeler.
HawaiianSteak@reddit
Depends on the car but an Accord (don't remember the year or trim level) was tested and found that for that particular test car the sweet spot was 52mph.
anallobstermash@reddit
All cars are different.
Raise your tire pressure for a decent mpg gain.
Gold-Leather8199@reddit
Fuel efficiency and speed done go together, go buy a 3 cylinder little bitty car and leave it in a garage
RuneScape-FTW@reddit
For both my CX5 and Ford Escape, it seems to be mid-60s.
madderhatter3210@reddit
55-65mph, behind drag, cruise control one, my ‘16 Corolla s used to get almost 50mpg when it was rated at 30highway. Have gotten spikes of up to 60-70 for a short while, idk why
JellyfishQuiet7944@reddit
I wonder if they factored camping in the left lane.
SofaKingWetarded-@reddit
55 stay alive, 5t is how I drive. My father gets in the car, 105 is how I drive...
grafixwiz@reddit
Make sure all of your tires are inflated to the proper pressure, use ECO mode (if equipped), and cruise control set at 55-60mph
SillyAmericanKniggit@reddit
The slowest speed you can travel in your highest available gear without lugging the engine.
In most of my cars, that has been between 40-50 miles per hour. Stick to the back roads if you want to go that slow, because it’s in the “dangerously slow” category for most Interstate highways.
The biggest boon to fuel economy that is practical in real world driving is to look farther ahead and leave a larger following distance. Basically, drive so that you hardly ever need to use your brakes. Coast early and coast often, and don’t accelerate towards a stop.
I am currently averaging 49.3 miles per gallon in a car that’s only rated for 42 on the highway. That average is over 10,835 miles. I drive whatever the speed limit is. Im not doing 50 in a 70 zone to save gas.
tactical_sweatpants@reddit
Depends, I have a fairly aerodynamic sports sedan and for me 65ish is the sweet spot but in my 89 f150 brick I get the best mileage around 50-55
tnseltim@reddit
In my ram the mileage drops significantly at speeds over 58/59 mph. I can get 20-21 mpg at 56-58 mph, I’ll get 14 mpg or so over 70 mph. Even so I don’t have the patience to keep it below 70.
Ok-Idea4830@reddit
Is this the 1st time behind the wheel of a car? Just stay out of the left lane.
No_Candidate_3676@reddit
Not condoning speeding at all, but the 2013+ dodge darts get phenomenal mileage at 75-85 mph, close to 50-55 mpg with the 6 speed manual
PowerlineTyler@reddit
In planet earth metrics, 90kmph
In ‘murica id say like 50-55ish?
Ziazan@reddit
It absolutely depends on your engine and transmission and stuff like that, there's no one size fits all answer.
In most cases it's probably around 60mph, +/-5, for optimum mpg. But if you go too slow you'll have lorries overtaking you, which really isn't ideal. I'd just lock in at 70ish if I were you, the cost difference isn't that much but the time difference is, it's half an hour slower to drive 200 miles at 60 than it is at 70, not far off an hour slower to drive at 55.
You have to factor how much you value your time into the equation.
Maybe try locking in different values as an experiment and resetting the trip computer each day, you've got plenty opportunities.
CardiologistOk6547@reddit
Don't be one of those assholes that drive 12 mph under the posted limit just to save a couple of pennies on gas. You turn yourself into a road hazard.
kona420@reddit
Air resistance pretty much always increases with speed but there are lots of other non-linearities.
So it depends on the vehicle (and options), altitude, temperature, humidity. Higher density altitude, you can hit higher speeds with the same power. But at the same time the motor may be less efficient.
Taller gearing, larger motor, likely to see a higher highway cruise "sweet spot"
Whatever vehicle it is, the number will probably be around the lowest RPM you can maintain in top gear.
withpatience@reddit
Most cars are pretty efficient at 2k RPM. So top gear at 2k RPM would probably be the most efficient.
Also, keeping it around or under 60mph to lessen wind resistance is also important.
GuiGo_BA@reddit
That's the best answer, the key to have the best MPG is to find the maximum speed that you can get with the lowest RPM.
It's fairly simple: more RPM = more fuel.
I would like to complement saying that a 6 cylinder avalon maybe can keep less than 2kRPM at around 50mph.
So, find the maximum speed that you can keep between 1.5k and 2kRPM and you will have the best fuel consumption
Gutter_Snoop@reddit
Good ballpark answer, but I have to point out this depends entirely on your car.
In zero wind, my 4-banger Sentra gets best mileage at about 2200, which is about 60mph for it. My old V6 Equinox, it would be about 1800rpm, which would get me about 55mph. My mini-diesel pickup is about 1600rpm at 50mph. My old Pontiac G8 it was about 1600 at 60mph. You basically just have to figure out what lowest speed your vehicle will maintain at the lowest part of its power band.
Humble_Handler93@reddit (OP)
Thanks for the advice
the_Bryan_dude@reddit
My 98 Mustang GT got the best mileage at 90mph. 30mpg from Sacramento to San Francisco regularly. That's definitely not the norm. All cars have different spots.
CAStrash@reddit
Depending on the cars gearing, transmission and how flat the road is 55mph to 75mph.
The cars I had with 4 speed automatics were around 55mph, 7 speed auto's around 70-75mph.
squatcoblin@reddit
I know this wasn't your question but i feel its relevant to say that most fue is spent in taking off especially in traffic situations. You can save quite a bit just by slowing before traffic lights so that you don't have to come to a complete stop for them ." Hypermiling" is almost a sport in itself and there are many different strategies to stretch a gallon .
Vog_Enjoyer@reddit
My impression was slower is better mpg as long as you're rolling like 25+
The best my 99 bmw 540 would get is 40mpg going 40mph in 4th.
haus11@reddit
I’d ask what your time is worth? The difference between 55mph and 70mph is about 50 minutes over those 200 miles.
DBDude@reddit
It depends on the aerodynamics of your car, the efficiency of the engine at speeds, and whatever systems you have running that sap power from your drive system.
As an extreme example, say you have a very small and efficient drivetrain geared for high speeds, a very low drag car, and you want to blast the A/C and very powerful stereo the whole way. That last part is a constant drain on power continuously for the whole trip, so the less time the trip, the less drain there is. So go faster to reduce this drain, but pretty soon the higher aerodynamic drag will cancel out your gains.
PossibleMechanic89@reddit
Slowest speed you can go in the highest gear without the engine complaining about it.
crusty_grundle@reddit
I'm driving a VW Taos, doing almost 200 miles a day on the freeway. There is almost no difference in fuel economy between 60-70 MPH, but it is impossible to maintain that for any length of time in SoCal. Sometimes I'm going 35 and other times I'm going 75, but I average 37MPG with my commute and car.
Blu_yello_husky@reddit
It really depends on the transmission and gearing more than anything. Generally speaking, on your basic 4 speed OD tranny (most lower end cars on the road will have these), 55-60 is the sweet spot for best mpg. On older cars that have only a 3 speed, 45-50 is going to get you better economy. Anything over 65 and you'll actually be getting worse fuel economy.
daubs1974@reddit
I love a question like this. While saving up to buy my first house 25+ years ago, I was maniacal about expenses. I Brown bagged every lunch, I didn’t have cable television, I did have Internet, but not a cell phone. Driving my 1999 Hyundai Accent, 5 spd, no AC, I found my fuel economy was nearly 6 miles a gallon better at 55 miles an hour than it was at 65 track your mileage, and compare different speeds. In my opinion, 55 to 60 is probably where the sweet spot is. I also chose to bump my tire pressure to psi above the cold tire pressure recommendation on the label on the door jam. I was sacrificing a little bit of quality to gain a little bit more fuel efficiency.
OGKillaBobbyJohnson@reddit
Different depending on engine, transmission and gearing. The factual answer is usually the lowest speed that top gear will allow (without logging down if it's a manual)
Ok-Fox1262@reddit
In general, in your highest gear, when the Speedo needle is vertical.
This is not a hard and fast rule but appears to be true.
Sketch2029@reddit
110 MPH? Got it.
Ok-Fox1262@reddit
What are you driving? Here that's between 55 and 75 usually.
Elegant-Ad-3371@reddit
It depends very much on the car. As a very general rule above 40mph the biggest impact on efficiency is air resistance, which squares with speed.
Most cars have a sweet spot around 55-65mph.
55 will be more efficient than 65, but you'll need to factor in the time elements. 200 miles at 55 takes 3hrs 38 mins. At 65 it takes 3 hrs and 4 minutes.
speeding2nowhere@reddit
As fast as you can go without getting pulled over.
Time is money. 😉
50ShadesOfAcidTrips@reddit
There’s no real best speed for fuel efficiency. Read about hypermiling. It’s about reading the road and anticipating traffic. Avoid heavy acceleration and breaking. Also cruise control is terrible for fuel economy.
Humble_Handler93@reddit (OP)
That’s interesting I would have thought cruise control would be more efficient that good good to know
50ShadesOfAcidTrips@reddit
Yeah it surprises a few people. Cruise control keeps the car at a set speed at a disregard for anything else. I remember a Top Gear episode where Jeremy Clarkson drove a diesel Audi A8 from London to Edinburgh and back (800 miles) on a single tank. Obviously a completely different car and country but the technique is the same. Give it a watch as it’s highly entertaining.
Gutter_Snoop@reddit
They fudged stuff on that show a lot. I'm fairly certain Clarkson ran it dry and they had to give him a shot of fuel to get across the line. That's not to say the car isn't capable of 800mi on a tank, I'm just saying Clarkson wasn't lol
50ShadesOfAcidTrips@reddit
Top gear fudged a lot of stuff but never those challenges. Besides if he failed it would’ve been fucking hilarious for an ending.
Gutter_Snoop@reddit
What makes you think they never used editing to make a good story?
50ShadesOfAcidTrips@reddit
Oh I’m not saying they never edited it to make a good story. The presenters have stated multiple times that the cross continent races/challenges were planned to be extremely close but the results were never fudged. They’ve said this multiple times in print.
jonnyt88@reddit
I've never seen but I have a Diesel A8, and its ridiculous the mpg it gets for the size/power/AWD once its up to speed. Low 40s mpg with a 23 gal tank. My bladder always looses.
That said, my previous VW TDI cruise was a good 4-5 mpg worse when I used cruise. No one could ever tell the mechanical explanation to why other than it your foot would tend to stay steady with ups/downs in the road where as cruise would be lightly braking/accelerating.
DolbyFox@reddit
Even for an early TG challenge, that's an understatement. It's rather hilarious
50ShadesOfAcidTrips@reddit
The funnier hypermiling challenge is when they try to drive from I think Geneva to Blackpool on a single tank. Still don’t know how Jeremy made it there in his jaaaaaag.
Mybadbb@reddit
How can cruise control be terrible for fuel economy? Using it on the highway keeps the RPMs consistent and higher RPMs = larger engine load = more gas used.
pogoturtle@reddit
Because it won't account for inclines or declines or even traffic. If you were on a 100%flat road it's good. But if you're trying to sip gas you'd learn how to gently accelerate downhill and gain speed to gain momentum going uphill without adding too much load or using too much gas.
Mybadbb@reddit
I guess that's relevant if you're somewhere that has a bunch of hills or mountains, but even still I'd imagine it's better to use cruise control anytime you're not in traffic or actively going up or down a hill.
Gutter_Snoop@reddit
So... middle of nowhere South Dakota then? Or central Texas?
Literally any hills or traffic will tank economy with CC. In the real world, best economy will be achieved with smart, manual driving. However, it requires focus, attention to detail and skill, so for some people, CC is still best.
rubenthecuban3@reddit
Yea sometimes cruise control tries to keep a certain speed during a hill making it shift to lower gear. If I was driving I could’ve accelerated more during the flat part and use less pedal during the uphill all using the same high gear preventing the up shift.
PK808370@reddit
The issue is if there are hills or any other thing that changes, or even the speed you set leaves the car at a less-efficient RPM. The issue is control - from OP’s car’s era, a stick shift is more efficient as well.
JCDU@reddit
*some* cruise is bad for MPG, some is designed to be very good at it, sometimes it's more efficient just because it holds a nice steady speed and changes speed quite gently, *good* radar cruise can be very good in some cases.
And there absolutely are better and worse speeds for MPG - wind resistance goes up exponentially with speed and really kicks in above about 50mph, but going too slow you're not operating your engine and drivetrain at peak efficiency either. Many auto boxes won't be locked up until a certain speed for example.
50ShadesOfAcidTrips@reddit
The cruise control on a 2002 Avalon is hardly the same as a 2024 Corolla. Even the newest ones get slightly worse MPG than hypermiling. It really makes a difference over a long journey.
JCDU@reddit
Depends how good you are at hypermiling and what your drive is like though - as I said, sometimes just the fact it holds a steady speed with no big changes can be worth it.
50ShadesOfAcidTrips@reddit
Not disagreeing with you there. But the only time I ever use the cruise control in a car is when the road I’m driving has average speed cameras on it.
PlsHalp420@reddit
Get a tool like torque pro and a cheap obd2 reader. Setup MPG on it. Adjust based on condition and feedback.
SignificantEarth814@reddit
Long distance competitive fuel efficiency guy here - there isn't a set RPM for max furl efficiency, its a set RPM AND TORQUE!!
Most cars don't display engine torque, but you can get this from the car engine computer a bunch of ways. But you don't really need to because all it really means is the engine has to be accelerating, going up a hill, or both. Any other condition such as flat ground constant RPM, the most fuel efficient gear is Neutral. You want to be starting at 50, slowly accelerating to 65, then putting it into neutral and coast back down to 50.
How a car coasts down is super important for fuel efficient driving.
Sketch2029@reddit
I'm not a competitive hypermiler, but I have played around with different driving styles in my own cars to see how they affected fuel economy and this sounds wrong. There is a set RPM for maximum engine efficiency, but drag plays a major function in overall efficiency so you can't discount speed unless you are keeping speeds below 50mph.
Acceleration will use more fuel than steady speed. In my experience, most cars will actually get better fuel economy by accelerating quickly up to speed so they spend less time under acceleration load. Additionally, when you decelerate in gear your engine goes into fuel cut where you use no gas (infinite fuel economy!). If you're in neutral you are still using gas.
I think the one time it does make sense to use neutral is long downhill sections through mountain passes. Just shift into gear and use the engine to decelerate if your speed creeps too high, then back to neutral.
SignificantEarth814@reddit
The second part is right, neutral down a hill is basically free energy, but if you're going too fast then slowing down using the gears is best. On some cars this will even cut fuel while the road spins the engine, making it more efficient than idling in neutral.
But on the first point, this is something a lot of people don't intuitively get about engines. There is an RPM where atmospheric gas has the best chance of mixing with fuel. The valves and everything is designed around that RPM, for a diesel its almost always 1800rpm, and for a patrol its usually low-2000s to 2800. But that says nothing about the amount of power, in horsepower or watts or joules whatever, that you get from that engine at that RPM. The engine can squirt in a little fuel, or a lot of fuel, at that RPM. How much depends on what the engine thinks the resistance to turning, a.k.a. load, a.k.a. torque required, is going to be.
So basically, and these numbers are made up for explaining only, downhill at 1800rpm the engine isn't squirting in any fuel. Flat land @1800 the engine squirts in say 20% of its maximum. Uphill, with a trunk full of beer, it may go up to 100% where you can't accelerate beyond 1800rpm even if you wanted to and any less fuel and you'll slow down.
So engines are most efficient at their rated RPM, and usually about 80% load, which is to say a little more accelerating could happen, but the car is definitely struggling. Its under load.
For this reason cruising at a set speed is not fuel efficient, because the engine will be under very light load (and usually too high an RPM). It isn't accelerating, or overcoming a hill (gaining potential energy) so its basically only operating to push air out of the way so its only at 20-40% load/resistance of its max capacity, and that's inefficient.
Put really simply, if you have a 100hp engine and you aren't asking from it 80-100hp of work, its oversized and inefficient for the job. To be more fuel efficient, you use the engine in its sweet spot, turn that fuel into momentum as efficiently as possible, then disconnect the engine from the wheels to prevent it slowing you down. This is called "pulse and glide" in the hypermiling community .
perfectly_ballanced@reddit
Depends on a lot of factors, but basically it's the lowest speed you can drive in your highest gear, it might be 65 mph, it might be 40 mph, but generally it's between 45 and 55 mph
bigtim3727@reddit
45-65, sometimes rpm dependent.
Like my 2018 F150 will be at ~1900 rpm at 80MPH, and the fuel economy isn’t great, but at slower speeds, esp when it’s at around 1500RPM, it will get in the mid-high 20s all day
My 2012 Jetta GLI on the other hand, it’s at like 2600RPM at 70, and it gets good fuel economy, but under 2K rpm, at speeds between 45-60, it gets really good fuel Econ; high 30s
slavabien@reddit
Try to think more in terms of RPMs. Are you pushing it at 65? More than 2300 RPM? You’ll want to keep it under 2k RPM, so whatever that translates to on your vehicle. Cruise control may not help this because the priority is speed and not revs.
Sketch2029@reddit
This really depends on the vehicle. 2K RPM in top gear would be around 45 MPH in my car. Not good for highway driving. It would also be so far out of the power band that I would have to open the throttle a lot more to maintain speed up hills than if my RPMs were higher. Low RPMs help, but having to make minimal adjustments to throttle position helps more. This is the main advantage of using cruise control.
carguy82j@reddit
Depends on the car but 55 will do it, but you will piss everyone off in some areas
lellololes@reddit
Each car is different, but my general experience is that slow highway speeds tend to be pretty optimal.
I hit 36-38mpg in my Mk7 GTI on a gently driven trip on country roads that averaged more like 45mph - at 70mph it'd be closer to 30-32.
I had a Civic Si that didn't seem to benefit as much from slightly slower speeds.
I had a 1.4T Jetta that was pushing 50mpg on a flat stretch of 70mph highway.
Talentless_Cooking@reddit
Drive the speed limit and don't treat the pedals like on off switches. Pedal control is your best friend for fuel economy, driving on the hiway you have to do the speed limit and keep up with traffic, otherwise keeping the revs comfortably low will help with fuel economy.
CarLover014@reddit
General consensus is around 55-65 mph for most vehicles, but each vehicle is different. My Xterra will get its best gas mileage at 45 mph (because it's shaped like a brick). My Corvette on the other hand would get better mileage at 80 mph than at 60 mph.
Stooper_Dave@reddit
If your car has a tachometer, pay attention to it while crusing and find the spot where rpm is Low and the engine doesn't sound loaded when your on a fairly level part of road. That's your speed.
radonfactory@reddit
swap the v6 with a small tractor diesel engine https://www.youtube.com/watch?v=qqmFebuDFvQ
Equivalent_Papaya893@reddit
I go 80 mph behind a bigger car and blast my horn so he'll speed up. Use him as my draft car.
Garet44@reddit
In your car it will be the slowest speed your torque converter locks in top gear. Likely 45-50 mph will be best for mpg, but it will not start falling off a cliff until you get over 65-70 mph.
If you really want to know the correct answer, you need to get an OBD-II reader than the read live data from your maf sensor to determine actual instantaneous mpg. Start logging data, and go on a loop. A 1-2 mile stretch of high speed road between 2 roundabouts would be ideal. See what the actual mpg data is for different cruising speeds.
Ghia149@reddit
In a rather rudimentary general rule sort of way, driving at the speed where your car will shift (ATM) into and maintain it's top gear at the lowest RPM's is going to likely be pretty close to the sweet spot. Anything less than that and the car shifts down a gear and you aren't getting as far for each revolution of the engine (due to gearing), anything faster than that and you are doing more work than necessary to push through the air, remember drag is exponential so this drags down MPG very very quickly as you push beyond this spot.
This is without any evidence or testing or anything so your mileage may quite literally vary, but it would be a good general place to start. the more hills you have the more you will have to make decisions about how much speed to carry going down hill and how much to back off going up to avoid downshifting.
Now if you are driving a manual transmission... that's another story, bogging down the engine and giving it gas below where it makes power will be just as bad if not worse than higher RPM's in a lower gear, so that's where you need to have some sensitivity.
adultdaycare81@reddit
Funkyfookarate@reddit
Please stay in the far right lane, and if you are on a 2 lane road, let the mass of cars that will appear go. Good luck with your gas saving.
ExperienceNo7751@reddit
Top Gear, along with others put economy cars on a high-speed-ring specifically to find the best fuel economy.
They could get 40-50 with typical 4 cylinders by going about 40-45mph.
Mythbusters also did one on tailgating 18 wheelers. I have repeated their test results successfully. I’d advise jumping behind one and keeping the distance around 1-2 car lengths. I’ve gotten 10-15% better economy just being 2 cars back.
SeinfeldOnADucati@reddit
>What is the most fuel efficient highway drive speed?What is the most fuel efficient highway drive speed?
Bump drafting
glade_air_freshner@reddit
Whatever the sweet spot is. Every car has a sweet spot, but not all are at the same speed. Take it on the highway, and vary your speed until it feels "right". And by that I mean, when the car feels almost like it's carrying its own weight, with minimal throttle input. My Corolla is about 60 MPH, my old Civic was 70, and my Buick was 80.
Concrete_Grapes@reddit
If I recall, as an aerodynamic thing, anything above 45ish, is just a downward slope. From an aerodynamic perspective, I think I remember, for every mpg above 60 (to 70), you lose about 2 percent in mpg. In some cars or trucks, this gets way worse, due to how timing or air fuel systems work. In a 5.3 Silverado, it will run in 4 cyl mode all day at 65, but go 70, and ANY kind of hill is just going to throw it into v8. So, I can get it to average 26mpg if it never goes above 65, and 19 if I set the cruise to 70 on the same road.
The civil will get 60+mpg if we never go above 45, but, do 60, and it'll get 40ish. Do 70, and it gets 34.
Now, the tradeoff is time--once you figure out if your car has a drop off (65, 70, etc), and avoid that, it's about time more than mpg. Do I want to drive 45mph everywhere so the 2018 civil gets 60 mpg? Or, would I rather go 68, and draft larger trucks, and hover around 40?
dubalishious@reddit
Whatever speed you choose, cruise control/consistent speed is gonna help the most with mpg. Between 55-70 I don’t see too much of a difference.
RKEPhoto@reddit
"I can't drive 55!"
https://www.youtube.com/watch?v=RvV3nn_de2k
Scott-from-Canada@reddit
Get an OBD-II reader and see the instantaneous/average consumption, and base it off of that. Nobody here is going to have a real answer for you.
Beautiful_Ad_4813@reddit
Because I live in Michigan and people easily fly by at 75 +, I USUALLY I cruise at 65, and can get 600-625 miles out of my tank in my 15 Passat (gas). I also have low rolling resistance tires on this mid size sedan. Can’t bitch to much about that.
when I had my diesel Jetta, 65 mph and would easily get 750 miles out of my tank without much effort. On the same side of that coin, my Jetta Hybrid would crest regularly 500-550 miles out of a 10 gallon tank.
However, it greatly depends on the condition of your car, how well it’s maintained, and how much air in the tires plus if the alignment is correct
TruthImpressive7253@reddit
Highest gear lowest rpms
often_awkward@reddit
It depends on the vehicle and a lot of other conditions but you can be assured that the whole 55 mile an hour thing is mostly a myth and a really good example of YMMV.
TBH the best way to figure it out is to just keep your gas receipts and record the mileage but usually a clue has to what you're specific best efficiency is often going to be where the speedometer points straight up.
Another game to play is get in your highest overdrive gear, most cars just have one, and see what your speed is when you are at the lowest RPM you can manage in the overdrive gear.
We go on road trips that are 1000-2000 miles round trip several times a year but mainly in the winter because we like to ski and take our dogs but we live in a pretty flat state.
I drive a 2020 Chevrolet Tahoe. I have figured out that my most efficient speed when I have a full load with our giant box on top with all the ski stuff in it is between 70 and 72 miles per hour and also if I'm running 90 plus octane fuel.
Admittedly this sounds kind of weird but in my specific situation my engine has the ability to shut down half cylinders which bumps the fuel economy up pretty significantly. I have a flex fuel vehicle with a fuel quality sensor so I get more power available with higher octane fuel. This allows the vehicle to operate in four-cylinder mode at higher speeds. When I drop below 60 miles an hour it goes into the lower gear and spends more time in V8 mode.
I also have the benefit of two overdrive gears and depending on weather and grade I can run at the most efficient speed for my engine which is around 1200 RPM around 70 mph up to 75 but I hit a really significant drop off in fuel economy at high speeds so it's a lot of tracking and calculating.
To absolutely maximize - limit acceleration. Also, make sure your tire pressure is correct, your air filter is clean, oil is at the correct level, and you are carrying as little weight as possible. You can also get a little bit from making sure your car is clean so that there is not any extra drag.
WTFisThatSMell@reddit
Depends, my car gets 23 mpg doing 80 mph when I did 200 miles a day 5 days a week.
Would get 21 at 70mph.
Almost died doing 55mph because the limit is 65.
The trick is use the cruise control.
Hydraulis@reddit
It depends on the gearing, but for most cars, it will be between 60 and 80 km/h.
Almost all highways are at least 100 km/h, so that would be the most efficient without going under. Going over will absolutely consume more fuel, and by a big margin.
120 would easily increase fuel consumption by 20%. The faster you go, the worse it gets.
Rlol43_Alt1@reddit
My car loves 80-85.
realityinflux@reddit
If you drive as fast as your car will go, the trip will take less time and you will use less gasoline! SARCASM
SpaetzleX@reddit
My first car’s - 1992 Camry 4cyl manual - owner’s manual said in no uncertain terms that the faster the car went the better the fuel economy it achieved. I drive like an absolute maniac as a teenager and got 40+mpg on the highway.
I believe the Lexus - rx450hl - that I currently drive is similar despite the current consensus is about the ideal highway speed being 65. I drove an entire tank of gas at 80mph a while back and got 33 mpg, the best I’ve ever gotten
SuperNa7uraL-@reddit
Depends on how many speeds your transmission has. My Crown Vic with a 4 speed automatic was at higher RPM’s at 80mph than my Kia K5 with an 8 speed automatic. At 80 I can get near 40mpg. Slower might be a slight bit better, but the time savings is worth it more to me.
After-Chair9149@reddit
Depends on car. When I had my 2014 mustang v6, I usually got 22 mpg on highway, and 19 around town. I drove to visit my now wife and got 32 mpg in 6th gear with cruise control set at 80 mph on PA turnpike.
LossPreventionGuy@reddit
I have a hybrid that tracks mpg usage, and the difference between 65 and 70 isn't enough to care, but the difference between 70 and 75 is like 30 percent
Humble_Handler93@reddit (OP)
That’s good to know
Rapom613@reddit
Depends on the car, you’ll have to play with it to find out. For example with my Audi, I get the same MPG at 65 as I do at 90
Look into investing into something called a scangauge. It reads you MPG in real time, so you can figure out your best driving habit and speed to maximize efficiency
numbersev@reddit
Just stay in the outside lane at the speed limit and try to keep a good amount of distance from the car ahead (so even slower if need be). Only issue is cars merging onto the highway. You'd either speed up a bit, slow down a bit or move to the center lane (which is going faster most likely than the limit).
The important thing is to try to avoid braking and accelerating, especially more abruptly. That's where fuel economy dips. If you can maintain a consistent speed, that's ideal.
1CorinthiansSix9@reddit
consistent*
If you’re on rolling hills letting it dip 5-10 on the incline (consistent throttle) and letting gravity do its thing on the downhill (a little heavier on the throttle) is more efficient than cruise control
Hersbird@reddit
About 40-45 is the most efficient speed, but that's not highway speed. Just go the limit or the truck limit if there are multiple lanes.
PolybiusChampion@reddit
According to the Tesla’s I find myself behind in the left lane……64.75mph in a 65.
secret_alpaca@reddit
From personal experience with my specific car, 55-75 seems to yield the best mpg.