My truck is burning oil very fast. What could be the culprit?

Posted by hjjhjjnk@reddit | askcarguys | View on Reddit | 18 comments

TL;DR truck giving low oil after topping off with 3 quarts 2 weeks ago, and there’s no signs of oil loss under the vehicle. I have a 2015 Chevy Silverado 5.3L v8 with 150k miles on it. At 120k I had to replace the cats, and at 140k I had to replace the transmission. For the past 20k miles or so, I’ve had to top off my oil when I get to about 4000 miles after an oil change. Just toss a quart in and call it good. This past oil change, which I’m 2600 miles into, I had to add 3 quarts at about 2000-2100 miles and I’m already getting alerts that I have low oil again. This was only 2 weeks ago that I added 3 quarts. I can’t see any oil leaking while the vehicle is parked, and my exhaust isn’t heavy of white smoke or anything. It has to be burning off or leaking while I’m driving, but I’m just not sure how. I plan to take it in to the mechanic tomorrow If possible, but figured I’d ask for advice on what my problem could be.

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18 Comments

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omg4serious@reddit

for me, the cylinder bores were worn out and the piston rings were not completely sealed. this started happening for me around 70k miles, but got really bad at 95k miles, it was under warranty so they rebuilt the engine.

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Bulocoo@reddit

There's 3 ways in to the cylinder. Past the valve guides, past the rings or through the intake. Vapors get into the case past the rings during combustion. These vapors are collected, oil is separated and vapors sent to the intake for recombusting and exhaust. The vapors system can fail sending oil laden vapors into the cylinders. Fixing that is cheap compared to worn valve guides or broken piston rings. The only other place is a valve gasket failure and oil could go into radiator fluid. But by now you would notice oily overflowing radiator fluid.

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mrkprsn@reddit

Use Valvoline restore and protect oil

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IneedHennessey@reddit

Bad piston rings would be my guess

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Blu_yello_husky@reddit

Stuck rings, bad head gasket, internal leak at oil cooler. Basically all these options spell out doom for your engine and are gonna be pretty big $$$ to fix. Thats too bad for a truck that's barely 10 years old.

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WorthOutside6757@reddit

Change the PCV valve. It causes high oil consumption if bad.

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RampDog1@reddit

I'm going to guess if you had to replace the cats oil is burning out the tail pipe. The cats are catching it and will clog again. Any misfire codes on the cylinders?

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Viking2151@reddit

Yeah something is not right, probably related to the AFM, my 94 Suburban got a slight rear main leak and a small oil cooler line leak and I need to add maybe a half a quart of oil in it every 2500 - 3000miles and I thought that was too much lol.

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CalmDownChillOut@reddit

That’s way beyond normal oil consumption for a 5.3 if you added 3 quarts \~2k miles ago and it’s already low again with no puddles, it’s almost certainly burning oil internally. On a 2015 Chevrolet Silverado 1500 the two most common culprits are the AFM (cylinder deactivation) system causing oil to get pulled past the rings, or a failing PCV system built into the valve cover that can literally suck oil into the intake and burn it with little to no visible smoke. Less likely but still possible is worn/stuck piston rings at that mileage. I’d have the shop check the valve cover/PCV first (cheap and common fix), then look for oil in the intake and run compression/leak-down tests to rule out ring issues but either way, losing that much oil that fast means something changed and it needs attention ASAP.

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thePhoenixEatery@reddit

Yea what this guy said

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hjjhjjnk@reddit (OP)

I do have a question about the AFM system. I remember my friend disabling the AFM system with a delete kit. Would this be a fix, if the AFM system is in fact the culprit, or would the system still need to be serviced even if I deleted it?

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CalmDownChillOut@reddit

An AFM delete can *help prevent it from getting worse*, but it’s usually not a true fix once you’re already losing that much oil. If the AFM system is the root cause, what’s typically happened is the cylinder deactivation has already led to oil getting past the rings or through the PCV system, and that wear/contamination doesn’t just go away when you disable it. Deleting AFM (tune + hardware) can stop the weird vacuum behavior and future damage, but if the rings are already stuck/worn or the lifters/valve cover are part of the issue, you’ll still burn oil afterward. That’s why most people treat AFM delete as either preventative or part of a bigger fix, not a standalone solution. I’d still have the shop check the PCV/valve cover and run compression or leak-down tests first, because if it’s something simple like the PCV pulling oil, that’s way cheaper than jumping straight to an AFM delete or deeper engine work.

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hjjhjjnk@reddit (OP)

Thank you for the comment, I’ll be sure to mention that when I take it in.

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Kootsiak@reddit

I would personally just assume the oil burning is due to stuck piston rings and try running a few oil changes of valvoline's restore & protect oil to loosen them back up. The oil is good stuff and proven to be one of the few reliable methods to loosen stuck rings without pulling the engine apart. If it's not reducing the oil consumption by the end of the first oil change, you might have a bigger problem.

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justthefacts84@reddit

Rebuild or replace the engine ! That is your only options left !

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Familymanjoe@reddit

Try thicker oil unless you are replacing the vehicle. Compression test would tell you more but likely burning it up. Is it running efficiently mpg?

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hjjhjjnk@reddit (OP)

Yeah mpg is pretty good. I’m using 0w-20 full synth so it’s a pretty thin oil.

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Inevitable-Notice351@reddit

Maybe a bad timing chain considering your mileage. Mine started going bad at 146K and was burning oil like crazy.