1991 Ford F-150 dipstick smells like gas

I noticed a smell of gas on the dipstick when checking the oil today. Not noticeable unless you actually place the stick near your face to smell it. Problem?

Lets see , there is not supposed to be fuel in the area where the oil is so Yes , I would say that is a problem.

1 Like

I’d be interested on the mechanics reply here. This is an issue that new Honda owners are reporting now and I am trying to learn more about it.

My first guess would be a problem with the evaporative system. Possibly a charcoal canister saturated with fuel that finds its way through the crankcase ventilation system into the engine.

So it smells different than some time before?
Or is this the first time you’ve smelled it this way?
Sometimes people mistake the smell of normal combustion products for raw gas.

1 Like

For a 27 year old F150, my first guess is worn rings. How many miles? Is the compression ok? Any oil use?


Remove the vacuum hose from the fuel pressure regulator.


If gas leaks from this connection, that’s how gas is getting into the oil.


1 Like

My vote is for the fuel pressure regulator.

If it’s the original, it’s a wonder it lasted 28ish years.

1 Like

The regulators were a common problem on Fords 20 years ago. And it’s such an easy thing to test it would be smart to check it first. And whatever is the cause of the fuel in the crankcase an oil and filter change should be done before driving.

A lot of short trip driving can also cause this. If that is the case, change your oil by time and not mileage.

Next time the oil is changed, drain the old oil into a container and see if you notice anything visually or odor-wise unusual. Take a sample and let it sit overnight in a clear container, see if it separates into layers. Used motor oil tends to have an acrid odor, with perhaps a touch of gasoline smell. That’s normal to me. If yours has an unmistakable gasoline smell that way, or the used oil is separating into layers, probably needs to be figured out why. If the fuel trim data looked normal, my first suspect would be leaky piston rings.

If it does separate, that’s water, not gasoline.

Automobile oils tend to have a density in the 900’s (kg/m^3) range, gasoline in the 700’s. But the two might mix so well they wouldn’t separate into visible layers, never tried that experiment.

Yep, once mixed I doubt they’ll separate

If the piston rings were leaking fuel into the crankcase, misfires would be the primary complaint.

I guess we’ll never know, the OP has left the building…

That seems to be a trend here lately, one post and then off into cyberspace .