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Will engine oil mixed with gasoline ruin a car motor?

My son was low on gas one day and grabbed 2.5 gallon plastic container holding a mixture of gasoline and oil for the chain saw. Shortly there after the car began running harder and harder back firing etc. until it wouldn’t run at all. Our mechanic said there was a leak in the block (I think) and we’d need a new motor.



Is it possible the Oil in the Gasoline mucked up the motor to a point it created a leak in the block?



No, that is NOT possible…I dispose of two-stroke mix all the time by dumping it into my car and truck…A little “top oil” never hurt anything…

It may smoke and stutter a little bit, but it won’t cause a “leak in the block”. That can occur in very cold weather when your antifreeze is too weak, or you blow a head gasket, which may ppear to be a “leak in the block”.

Your son must have done something else to the car or the cold weather and weakantifreeze cracked the block.

Ask the mechanic to fully explain what happened and where the leak is.

P.S. I would never put an oil/gas mixture in a modern car; my 1948 Chevy in college, however, used so much oil that it might as well have had a 2 cylce engine.

I also dispose of my old 2 stroke oil in my car but I have never put 2 1/2 gal in an empty tank, I always do it on a mostly full one so I can’t say for sure.

If the catalytic converter was already marginally plugged the 2-stroke oil may have been enough to finish plugging it and causing a loss in power and possibly back firing. But a couple of gallons of 16 to 1 mix would not directly cause any mechanical damage.

High quality two-stroke oil uses ashless dispersants that leave no deposits or smoke…It burns very cleanly in a four-stroke engine…When diluted to 200 to one or more, it’s not an issue…

In this case, if the tank was empty or near empty, one has to assume the first stop was a gas station, so again, the chance of damaging the engine is remote or non-existent…

How do you put the phrases “I think” and “need a new motor” in the same sentence? Get clear with your mechanic on his diagnosis and then get a second opinion.

I think the two-cycle engine mixture may have at worst fouled your plugs.

The bottom line is that a little two-cycle engine oil in your gasoline in not going to ruin your engine.

I doubt very seriously there is a leak in the block and it would be interesting to know how your mechanic arrived at this conclusion.

You might also clarify “shortly there after” because to some people that can easily means weeks or months.

Get a 2nd opinion. Mechanics are drama queens sometimes.

I just used gas oil mix in my truck that was on E. I drove it an hour and a half home. Then drove around for a good half an hour after I got into town. My gas gauge was a quarter inch below E. Now this is all on gas oil mix mind you. I put twenty bucks and regular gas in my truck the next day and my truck runs fine like nothing ever happened. So I’m here to tell you putting gas oil mix in your truck whether it’s on a full tank or a empty tank anything it doesn’t mess your truck up. However it’s not something I recommend doing all the time cuz I’m world where of what prolong oil in my gas tank will do to my truck. But in case of emergencies and that’s all you got to use to get to where you got to go… Got to do what you got to do sometimes.

Gasoline diluted motor oil WILL ruin an engine and I’ve seen it a number of times. Gasoline is not a lubricant; period.

Diluted motor oil can scrub off crank bearings, cam bearings, cam lobes, and so on; and it will not affect the running until things go way south which may be soon or not so soon. The only way of knowing is to tear into it although an oil pressure test could be performed.
You may get away with a tiny amount of diluted oil on the very short term but that’s it.

I think Donell is talking about oil-diluted gasoline, not gasoline-diluted oil. Is that right or did I miss something?

@ok4450 they’re talking about using a gallon or 2 of 2 cycle gas in a car.

As long as the gasoline is added to the fuel tank and not the engine there should be no damage to the engine bearings.

Hi everyone, new member, first post, thanks for the help!

I did the exact same thing - I put about 2 gallons of oil/gas chainsaw mix in my empty 2004 Tacoma tank. I then went to leave home and realized exhaust was smoking badly. Realizing what I’d done, I then diluted with about another 3 gallons of pure premium, non-ethanol gas normally used for my ATV. Now the truck will start only when I rev the gas while firing the engine. I can drive as long as I don’t let off the gas completely- if I do, the engine immediately dies…

any ideas what might be going on??

Are you sure it was a oil/gas mix and not diesel ?
Was this premium fuel leaded or unleaded ?

40:1 oil/gas shouldn’t have smoked all that much.

It seems to have worked itself out!

Good deal. Maybe the issue was that the gas was old more so than the 2 stroke oil.