How Does Gas Get in Engine Oil?

by Alicia Crowder
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Minor Amount of Gas

The piston rings are seals placed tightly against the cylinder walls. These piston ring seals prevent the gasoline from flowing past the pistons and down into the oil. They do not, however, provide a perfect seal; thus, a slight amount of gas will find its way into the oil as a normal occurrence. This amount should be extremely minute, and such a small amount does not change the oil enough to cause any damage. Changing your oil every 3,000 to 5,000 miles or every three to five months ensures that it does not become a problem.

Two ways to tell if you may have a problem with gas in your engine oil are: 1. If you start to smell a strong odor of gasoline while you are driving. 2. You notice white clouds of smoke coming out of your tailpipe.

If a large amount of gasoline does get into the engine oil, change the oil immediately upon fixing the problem that has allowed this to happen.

Excessive Fuel

When a fuel injector is stuck open, the fuel will flood out. Gasoline will definitely get into the oil when this is the case.

If the fuel pressure in your car is too high (above 7 psi) that may cause gasoline to get into the engine oil.

Gas could also leak into your intake manifold if there is a carburetor problem.

An inoperative injector system can also cause this problem, because if the engine is not firing appropriately, the gasoline will end up running down the walls of the cylinders.

Check to see if the float in the gas tank is rising the way it should be rising or if it needs an adjustment. You will not be able to look at your gas gauge and get an accurate reading If the float is not functioning properly.

Your engine may be running rich, with too much gas going into the engine and too little air.

Check to see if the oil level might be really high. This can also cause trouble.

Check Piston Rings First

Any time you realize that too much gas is getting into your engine oil, you should replace the piston rings and then replace the oil. See if this helps the problem, and if it does not, then investigate the many other possibilities as to why the fuel is leaking into the oil.

Perhaps at this point do a compression test. Otherwise you can try getting your fuel injectors tested. Also check your spark plugs to see if they are good or if they might be misfiring.

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