1981 F-150, with a carbureted 302.

My truck's oil almost always smells of gas. The level doesn't change, but it has a noticeable smell to it. After changing my oil, the smell would be back the next time I checked the level. I just assumed it was due to an overly rich carburetor tune, and I just planned to live with it til I could fix it.

But then today I did a decent bit of driving and got everything heated up to around 180F, and when I checked my oil after I got home and let everything cool, the oil no longer smells of gas. Just smells like motor oil.

My truck is just now becoming my daily driver around my small town. I let it warm up for several minutes when cold, til it's about 100F. Could the fact that the engine rarely sees normal operating temps mean that the pistons, rings, etc. haven't expanded enough yet and are letting enough combustion gasses into the crankcase to cause the oil to smell of gas?

 

mine too was smelling of gas in the oil.

But i think mine is also from a richly tuned carb, and going through the oil breather cap tube.

Mine was never super bad in the actual oil, just a very slight smell and oil level never changed.

 

Sounds like we're in the same boat. Or crankcase, I guess. lol

Does your truck see alot of miles, or is it like an around-town vehicle like mine?

 

Well its my DD so it runs every day. But i rarely drive it out of town as it doesnt get that good of gas mileage.

 

The engine not reaching full operating temp, combined with a rich condition, can lead to the gassy smell in the oil. Getting it fully warmed up, and the smell going away, is a good thing. If the smell was noticably stronger it could point towards a bad fuel pump leaking fuel into the oil. Not a good situation......

 

Yupp, your truck is running perfectly fine. Gas in the oil is actualy a pretty normal thing if you never let the engine reach full operating temp. All the cars at school (all post 2000) always have gas in the oil, just cause they get run like 10 minutes at the max.

When the engine warms up, the gas in the oil starts "boiling" off and gets sucked back into the intake via the PCV so it can be burned.

Also, on the same note, if you happen to pull your oil filler cap off, and it's got a greyish sludge, it's basically the same condition, just moisture instead of gas, which should go away once you allow the truck to heat up properly.

 

Before you assume you've got gas in the oil, spend fifteen dollars and get an oil analysis at your local Caterpillar dealer. It might save you some worry.
Cat has a first class lab and they're reasonably priced.

 

Engine driven fuel pumps can leak fuel into the oil.