Pros or Cons for adding 91 in an 87 engine?
Posted by Interesting_Coat2763@reddit | askcarguys | View on Reddit | 79 comments
As title, gas prices here in upstate NY have reached the point where premium gas (4.65/Gallon) and regular 87 gas (4.65/Gallon) have the same price so i was wondering if there were any benefits for putting 91 in an 87 engine? perhaps to clean the fuel injectors or whatnot.
experimentalengine@reddit
If your engine is tuned for high octane (as in the manufacturer tells you to use it), you need to use it so you don’t have excessive detonation. If that is not the case, you don’t need it, and it doesn’t provide any benefit.
Detonation resistance is the one and only thing high octane gas provides.
StJe1637@reddit
Higher octane fuel is slightly more fuel efficent
coreyjdl@reddit
No
Hoopajoops@reddit
Eh, it's possible that it becomes less efficient. Some companies increase octane by just adding more ethanol, which is less energy dense than gasoline
experimentalengine@reddit
By itself, no. As an enabler for higher compression ratios? Yes.
Yakker65@reddit
This right here.
Blu_yello_husky@reddit
It'll burn faster and waste more gas. 91 has no benefit unless its being used in a car that actuaply needs it. Otherwise youre just burning money.
sk1fast@reddit
You’ll only see a benefit if it’s 91+ recommended or required. From what I remember Ascent is only tuned to take 87 octane.
hatred-shapped@reddit
Pro? Zero.
Con? Zero as well. Just extra money, that's all
288bpsmodem@reddit
Slow down, that might not be true. Where i live premium has more detergents and sometimes doesn't have ethanol. This includes top tier gas as well. Also there are a few instances where 87 might knock a bit, like towing or a large inclined drive...so premium would def help there. If it's the same price it's a no brainer to go premium
aquatone61@reddit
Sometimes doesn’t have ethanol? It either does or it doesn’t…….
jnyc777@reddit
Depends on the brands and locations, in Canada ethanol free is hard to find, in the states it may not be
aquatone61@reddit
It can be found some places in the states but if a station has it that usually doesn’t change…… it’s not like all of a sudden they switch from one octane to another on the same pump.
jnyc777@reddit
I agree definitely not on the same pump for the same octane, I think he meant some gas stations will have ethanol free and some won’t
Minisohtan@reddit
When I get 91 at kiwk trip, it comes out of a special red handle because it's non-oxxgenated and for off-road or recreational vehicles only, which I've looked up means no Ethanol. Other places have ethanol blended in their 91. I think state law requires ethanol for emissions or something.
jnyc777@reddit
Ok and is that federal or state dependent? I know California for example is strict as hell, but are other states more lenient?
Minisohtan@reddit
I think the red handle, off-road only is Minnesota law
jnyc777@reddit
Whoa ! Surprised, stricter than cali sounds insane to me lol, mind you corn farmers lobbying makes sense though !
Minisohtan@reddit
It's definitely not stricter in the general sense than cali. Just more lobbying to make sure ethanol gets used
jnyc777@reddit
Fair, just to add to the conversation, according to Google did you know that ethanol is 30% less efficient but reduces tailpipe emissions by 40-50%
objective_opinions@reddit
It says “up to 10%” for a reason. Depending on the refinery that day it could have less. It used the be that 91AKI averaged around 6% ethanol. Not sure where it hovers today.
aquatone61@reddit
Yes, it says up to 10%. A pump that says that will say that, it won’t switch to non ethanol for a bit and then switch back.
LimeDry7124@reddit
True. It has it's own nozzle.
Most-Description4665@reddit
The stores around me are all 87E, 89E, and 91 clear no ethanol. The larger cities and urban areas have 93E which is just 91 clear with 10% ethanol. I hauled fuel for 5 years so I've seen it all.
LimeDry7124@reddit
Shell here in Illinois has two premiums one with 10% ethanol, the other 100% pure gas.
288bpsmodem@reddit
No. Some pumpsnwhere I live it'll say ethanol up to 10% on 2 pumps and the premium it won't say that.
aquatone61@reddit
Okaaaay, so then premium doesn’t have ethanol at those pumps. It’s not like they switch what kind of gas is in the ground……
Jacklunk@reddit
Upstate Ny you don’t always get 93 but you can get non ethanol 91.
On my ‘16 jetta I see a difference of 2-3 mph more with the non ethanol but with my ‘19 Tiguan no difference.
hatred-shapped@reddit
And that's region specific not the blanket answer the person is asking.
GaryO2022@reddit
I don't know where in upstate ny you are but here in Central NY 91 is over a dollar more a gallon then 87.
Interesting_Coat2763@reddit (OP)
Im also in CNY, and it turns out that someone in the gas station fucked up and set the wrong prices. They changed it this evening when i drove by again. It is now 4.05 for regular and 4.65 for premium.
GaryO2022@reddit
Stewart's gas station in Waterville. $4.199 for 85 $5.099 for premium on Saturday.
funkymonkey1002@reddit
If the ascent has the 2.4 turbo motor which I believe is the only option, I would always put 91+ in it.
Interesting_Coat2763@reddit (OP)
The manufacturer guide is for 87 tho?
Tony-cums@reddit
No. 91 doesn’t clean anything.
It burns money. That’s it. Complete waste unless your engine REQUIRES it.
pimpbot666@reddit
And I’ll add that 91 doesn’t burn any cleaner than 87.
An engine can be tuned to take advantage of higher octane gasoline, but there isn’t much difference, except some turbo engines can run higher boost for better efficiency and output.
dlsAW91@reddit
Anecdotal I know, but my work van had a cat going bad that would throw a check engine light on 87. If I filled it with 91 the check engine light would go away until i put 87 in it again.
288bpsmodem@reddit
If I go to shell, 91 has more detergents than 87. Is it worth the increase in price for me? Prolly not, but if it's the same price? I'm gonna buy it.
dlsAW91@reddit
Nothing unless your car can account for different octane levels. It may burn slightly cleaner but that’s anecdotal at best.
If it’s the same price, there’s no downsides really but the gas station selling both for the same price sounds like a pricing error
Busy_Account_7974@reddit
No, unless you got $$ to literally burn.
StJe1637@reddit
He's saying assuming its the same price
StJe1637@reddit
If its the same price you may as well get premium since it is more fuel efficient by \~5% or something
SirWillae@reddit
Pointless
Equivalent_Thievery@reddit
Modern cars are designed to adapt to different fuels, to a certain degree. Most cars will make more power on higher octane, though almost an imperceivable amount in most driving appliances.
Do you need to run higher octane? No, absolutely not.
Unless you're driving a legitimate high performance vehicle, just run the lowest octane your manual says your vehicle can take.
Apprehensive-Cycle-9@reddit
Yeah the Ford 3.5l turbo is a good example of this (really all of ford’s turbos) where it will make more horsepower with higher octane. Still really only useful to use premium when towing as it helps keep the engine cooler as well
Equivalent_Thievery@reddit
Yes, most turbo vehicles will make more power on higher octane.
And correct again, towing in most vehicles puts more stress on the engine and causes more misfires and timing retardation.
Equivalent_Thievery@reddit
Amusing to get a downvote on this, it's fact.
FitConsideration4961@reddit
It would only benefit if Subaru tuned the engine to also accept premium. You’d have to read the owner’s manual. Surprisingly, some manufacturers make engines that can utilize both, Ford’s ecoboost engines and Mazda’s 2.5 turbo. I belive Honda as well for their 1.5 turbo. But some engines run exclusively on 87, like VW’s 1.5 turbo.
u3b3rg33k@reddit
the ascent has a DI engine and a turbo, so it's entirely possible for the ECU to be watching the spark plugs to ride the edge of timing. in that case, higher octane would let it run more advance, meaning it could run less rich when you're "on it" and get better MPG.
otherwise, no.
NecessaryEmployer488@reddit
91 is kind of high. It burns cleaner and hotter. It's probably less ethanol. If it does not increase your mileage, don't use it. I generally use mid-grade. Sometimes it will help remove the check engine light caused by catalytic converter going out.
ValuableInternal1435@reddit
91 is often ethanol free. It does not burn hotter, in fact quite the opposite. I've noticed about a .5mpg increase running 91 octane in my 05 silverado lq4 compared to running 87, the 87 is e10, the 91 is presumably ethanol free (but I don't know for sure). Unfortunately the mpg increase is not worth the extra 60 cents per gallon. The truck also seems to run slightly better on 91. At 12.8mpg running 91, the cost associated is the same as getting 10.5 on 87. 12.3mpg on 87 hurts my feelings though (and wallet).
No_Zookeepergame5190@reddit
There's more ethanol in the gas to bring up the octane.
Coolmacde@reddit
Pros none. Cons are you're wasting money .
Ashton-MD@reddit
Shell top spec will have more detergents and additives that will clean out your engine.
Beyond that, you’re not using the correct spec for your car and are wasting your money. Given the situation, check your retailer first — a modern shell sourced fuel is arguably the best on the market. I’m sure there are other food retailers for fuel too but I don’t know them as well.
By contrast, putting the cheap stuff into a high octane engine, the fuel will ignite too early, killing fuel economy, performance and longevity over time.
tads73@reddit
Im hearing when 15% ethanol blend is allowed in may, the only way to avoid it will be to by 91.
91 could be something you use on an intermittent basis, but just a waste of money on a basic engine.
Higher octanes are used to prevent knock in high compression engines.
otterland@reddit
If you are buying top to your gas, all of the gas has the same amount of additives. It simply doesn't matter. But I would just use 87 on principal because that's what the car is designed for.
Eagle_Fang135@reddit
88 in a 91 engine it will “ping”, more noticeable on acceleration or with a load.
91 n an 88? Nothing.
CaliDude75@reddit
I would only use premium when it’s “premium recommended” or turbocharged engines. A lot of the newer turbos say they can run 87, but you won’t get the full rated power.
UncleSlayton77@reddit
If your owner's manual says 87, use 87. The only verifiable thing I've seen is that Shell puts more of their V-Power Nitro fuel cleaning additive in their premium than they do in their 87. So if you have a Shell offering premium for the same price you can burn a tank of 91 for cleaning (it actually does make a difference) then go back to 87. If the car was designed for 87 it will run better on it. On a '21 I'm sure if you put premium in it the ECM may test the limits of the ignition timing via knock sensors and advance the timing a little more but probably nothing you could feel.
Millennial_Falcon_85@reddit
Look up the compression ratio of your engine. If it’s 10:1 or higher, you will benefit from higher obtain gas.
truisluv@reddit
I bought a new car and googled whether I should put premium in and it said it would be a waste of money and to use 97. It says the same for your car no benefit. It is designed for 87.
RingOk664@reddit
Don't bother. Unless you have a high compression high performance engine, you're throwing away money. Here in SoCal, just paid $6.79 for regular.
PoopSmith87@reddit
You dont really notice any difference with cars... but there is probably a nearly imperceptible power and economy loss.
You do notice this on smaller motorcycles because there is so much less power and so much more connection to the vehicle. I was putting 93 in my DR650 until I read it was made for 87, switched over and it was a mild but noticeable difference in acceleration and a bit smoother at highway speed.
MansomeHan@reddit
Buy your gas at Top Tier certified brands. Higher octane adds nothing.
hexadecimaldump@reddit
There are no more cleaning additives in 91 than 87. It is just the octane number.
Octane numbers are just how much pressure is needed before gas will combust. Cars with higher compression ratios may need higher octane to prevent preignition due to the added pressure. Octane does not mean better or higher quality or anything like that.
Hot_Block_9675@reddit
Lets get one thing perfectly clear. Higher octane gasolines do one thing - prevent pre- detonation in engines that require it - typically those with higher horsepower and compression. That's IT.
My V8 Mercedes SPECIFIES 91. I've run 87 for FOURTEEN YEARS and 140K miles with no issues. Why? It has a knock sensor (like 99% of cars on the road today) and will retard timing instantly so there is ZERO pre-detonation.
Do I have less performance? Yes, and I can feel it. So what if I get to a stoplight .5 seconds later than with 91.
The only time I use 91 is if I'm towing my travel trailer or climbing serious mountains in hot weather. Both scenarios require more power and higher octane.
pimpbot666@reddit
Buy a bottle of injector cleaner and run it through the tank when you get your oil changed. That should keep things healthy.
Berryman Chemtool B12 is good stuff.
Chevron Techron and Lucas FI cleaner are also good.
Advanced-Elk-7581@reddit
I don't think your pricing is correct. 91 is NEVER the same price as 87. You are smoking something.
AbruptMango@reddit
Higher octane fuel than your car calls for has no effect.
red18wrx@reddit
Pros - nothing
Cons - it's more expensive
Flenke@reddit
No pros, con is you're wasting money
Archieaa1@reddit
In some cars the engine computer is smart enough to adjust timing allowing you to get more power. Remember that all octane tells you is how much pressure you can place on the air fuel mixture under before to combusts from compression.
Diligent_Bat499@reddit
Use a can Techron instead
Rough_Cancel7265@reddit
No benefit don't bother
StopLookListenNow@reddit
I used to do that and checked the cost / mile of every tankful. Then I wondered about the possible difference in compression and decided to just use the recommended fuel.
qkdsm7@reddit
At the same price, if the 91 happened to be ethanol free---that would be more btu per gallon and conceivably a decent better more MPG....
I see nice gains any time I spring for ethanol free.
MaximumDerpification@reddit
If your car is designed for 87, use 87.
If you want to keep the injectors clean then buy your 87 from a good gas station that adds detergents.
The only time running premium is beneficial is if your car is a higher performance model that is designed (or tuned) to run premium... some require it, others use a knock sensor to push the timing in order to make a bit more power on premium fuel.
guyfromthepicture@reddit
No real upside. It just handles heat better but if you aren't detonating, it's not a problem. You could probably advance your timing more.
Maleficent-Beach-572@reddit
Zero benefit.