I have recently done an oil change on my truck and my oil was overfull and mixed with gas (strong odor). After putting 50 miles on it, my oil is black and smells of gas again. I am sure gas is leaking into my oil but I'm not sure what this means. I've sea-foamed it this morning and changed the oil again after cruising around today. I only get around 5mpg in town and about 11 on the highway.
My transmission is freshly rebuilt, but other than that I've not changed anything recently.

Any suggestions?

 

could be clogged cat, leaking injector, bad o2. something is dumping way too much gas in it. at 5 mpg i'd guess a stuck open injector.

 

would a stuck open injector leak gas into the oil? I'm unfamiliar with the internals of an engine (*sigh* I know).

I'm pretty sure I know where the actual injectors are and may be able to replace them myself. Would help if I knew this was the problem...but any help is appreciated.

 

Man ... gas in the oil ... that is a poser ... used to mean a ruptured fuel pump diaphragm ... but now ... ummm ... might be an injector stuck open but no CEL for a misfire??

I'm gonna have to think a while about this one.

Gotta be something with the emissions control ...

 

i think it would. the diesel guys are always complaining about it on the cummins. fuel pump pressurizes everthing under relatively high pressure. injector is supposed to be normally closed, and then under computer control, open for a few milliseconds at just the right time for the intake stoke to suck it into the cylinder, and then immediately burn it. its multiport fuel injection so there is an injector at each head port. if the injector is stuck open, then its spraying or dribbling fuel all the time, which would wash past the the rings and into the oil.

you might be able to pull the plugs and pick up on one being richer or dirtier than the others. that would probably confirm an injector. otherwise, i'm not sure how to prove it. i got a feeling bill's going to come up with something though.

 

I had a guy at the oil stop tell me my oil smelled like gas about a year ago. My MPG was still fine and my oil level was fine. I think this was when my plenum gasket started to go on my though. If the intake could suck oil in to it's self could the engine also suck gas in to it's self?

 

i don't think so. the plenum is a low pressure area, which will suck in oil if the belly pan is leaking. the injectors are all the way down at the head ports, which is the source of the vaccum. i can't see the gas escaping from the low pressure plenum. i think it can't go anywhere else but down in the heads.

 

I have the same problem. I smell gas in my oil and I'm losing oil somewhere. I haven't been able to find any leaks around the engine.I have a '96 360 4x4 with 136,000 miles on it. I just changed the fuel pump due to a bad sending unit. The timing chain was replaced when it jumpedteeth on the sprockets a few months ago. The gas in the oil predates the fuel pump and timing chain mainenance. I've listened to the fuel injectors and they seem to be clicking away with no hiccups. The gas in the oil is causing my oil to thin out and give me oil pressure problems. A friend has suggested the intake plenum is a strong candidate for this problem. Your thoughts?

Thanks,

Mac

P.S. I now have the default AC defrost condition problem again. I suspect the guy who replaced my timng chain might have been a little careless. I had to take it back to him before for this after he worked on my truck. Didn't have a problem with the ACbefore he worked on it.

 

I don't think it would be a plenum gasket either. I had mine replaced a few months back with parts from Hughes. So that's all solid. And only last week did my oil light flicker and come to find out my oil is full and not low at all. The gas would be going into the oil at a different point.

 

I agree with dhvaughan and Aubrey, the high pressure fuel from the injectors isn't going to go towards a low pressure zone like the intake manifold and then leak into valley. It could definitely be a stuck injector which the gas mileage your getting but you should at least hear the engine running rough at idle...unless its slipping by the intake manifold gaskets, the injectors are sitting right on top of them.

The bright side of this problem is that, unlike oil with multi port injection there are only a few places where gas can be leaking into the oil. Follow Dhvaughan's advice and pull the plugs looking for one that is clogged with unburned fuel.