Oil smells like gas...

Not open for further replies.
Dec 31, 1969
Things just keep looking better and better for this engine.
4.0 Jeep engine...oil changed after 500 miles because the former owner abused the hell out of it. Oil is black, but that is to be expected, and I can tell the engine is getting cleaner. Now I can tell the oil smells pretty gassy...after only 500 miles. I know this is often from the rings/cylinders being worn out, but are there any other causes? Maybe a problem with the PCV system?
Get a new PCV valve right away to rule that out. Sounds like it needs a ring job at least. What kind of power are you getting? What is the oil pressure running. Gas in the oil is not very good.
It runs surprisingly well, and I don't think it burns any oil...other than what it spews out of various orifices.
Oil pressure? Well, that's broken too.

Originally posted by MarkC:
How old is your Jeep? How many miles?

It's a '90, with 99k, so the rings should be just fine considering this engine normally lasts 300k+, but as I said the former owner shouldn't be allowed to own cars.
I would run a UOA and see what it shows. I don't get too worried about that smell because it's common smell with my truck (Ford V8 / 127k miles) begining with the first oil change. Everytime I change the oil it smells like gas. UOA's have been flawless with this engine - so therefore I don't worry about the odd smell when I drain the oil.
Does it by chance have a mechanical fuel pump? Years ago had a mechanical fuel pump go bad and dump ALOT of gas in my oil.
I have the same engine with 170k miles, and the same problem. In '90 Jeep was using electrical fuel pump, with seq. port fuel injection.

The 4.0 is bullet proof, but its PCV system SUCKS. It easily clogs, don't know of a permanent fix. If you are getting a lot of oil on your air filter, then the PCV sytem is most likely clogged up. This could be the cause of your problem, as mentioned earlier. Also, if the origional injectors are still in use, that could contribute to your problem as well, as mentioned earlier.
There isn't a car that I've worked on that had oil that DIDN'T smell like gasoline. Gasoline is very strong smelling. Only a UOA would prove that a bad % is in the oil.

Start with a compression/leakdown test to rule out a tired engine. Don't forget the PCV/leaky injectors that have been mentioned. Check/change the plugs, timing, fuel/air filters(could be clogged), 02 sensor......and any other maintenance.
I think Russell is on the right track. I had the same thought when I read your post. I would also check for a leaking injector or anything that would allow fuel to get into the cylinders after the engine is shut down. The world's best rings will still allow gasoline to eventually pass by, if it sits there for long enough.
Not open for further replies.