Gas scent in oil

Messages
4,450
Location
Kuwait
I never really allow my engine to idle, other than a minute or two at 1 traffic light before I hit the highway, and my driving habits have not changed since I last changed oil 2,520 km (1,575 miles) ago. Driving is 80% highway and 20% city at worst, and the vehicle barely ever sees city driving. But when I pull my dipstick, there's a faint to partially strong gasoline odour in the oil. This wasn't something I've experienced before, and I'm wondering if the fact that I switched to a thicker oil (+20 weight) have anything to do with it. This is also the first time this engine sees Group IV oil after a few ARX treatments, and I used a thinner oil before. Reason I switched to a thicker oil is to temporarily reduce burn off until I get my valves, valve guides and seals replaced. So far, it hasn't burned enough to actually make a difference on the dipstick. With same weight Group II oil in the past, I would have to add a full quart by 2,500 km. I suppose synthetic not thinning down as fast in intense heat has its benefits as I thought. But the gas smell has me a bit worried. Any idea what could possibly be the cause? Engine in question is a Mitsubishi 3.0 V6 12-valve. Thanks!
 
Messages
1,347
Location
wytheville, va
This was a problem in my wife's 97 LHS (Chrysler)... and I ended up replacing the fuel pressure regulator to solve the problem. The oil had gotten so thin that it would drip like water off the dipstick, and oil was seeping out of the engine seals and you could smell the gas when you raised the hood. I guess the engine got a good flushing during that phase of its life. :D Replacing the fuel pressure regulator valve took care of that problem. :) Dan
 

Falcon_LS

Thread starter
Messages
4,450
Location
Kuwait
Thanks, Dan. I will be getting the injectors checked out, and I'll get the pressure regulator looked at as well whilst I'm at it. The oil doesn't thin down, but it's worth considering all possibilities.
 
Messages
25,046
Location
ON, Canada eh?
Falcon_LS, If you have a hand-held Vacuum gun, you can connect it to the Pressure Regulator to test it. Take the hose off, and plug it with a screw (This is a Vacuum hose) Then connect your Vacuum Pump Gun to the pressure regulator and with the car running pump it up. If the Idle changes either by stuttering or raises then the regulator is good and doesn't need replacement. If there is no change it is defective and needs replacement. (Cheap) These aren't a common problem at all on your vehicle, but were more for the LHS. Steve
 
Messages
2,248
Location
Chicago IL
If all the f.i. system parts check out, and you're still running rich, take a look at the coolant sensor. Strange as it may sound. If you're ECU gets misinformed, it "thinks" the engine is running cold and needs a richer mixture.
 

Falcon_LS

Thread starter
Messages
4,450
Location
Kuwait
Got it sorted! Believe it or not, it turned out the be the thermostat! Never would have imagined that being the cause...cheap replacement as well. \:\!
 
Messages
39,806
Location
Great Lakes
Just FYI, it doesn't really take much fuel in oil to be able to smell it. Most of the time it's normal. My oil often smells of gas, but the UOA never reveals any excessive fuel dilution.
 
Messages
19,479
Location
Chicago Area
Weren't there any codes with the cold coolant temperatures and over-rich condition? No other symptoms besides a fuel smell in the gas? BTW, your gas mileage is about to go up!
 

Falcon_LS

Thread starter
Messages
4,450
Location
Kuwait
Pete, this was actually the first time I noticed it. Usually, when I pull the dipstick out I check to see if it smells of gas and there was a very faint smell before. Recently, it got stronger and became a cause for concern. Mechtech, there were no other symptoms. But when an OBD-II system was plugged in, coolant temperature was at 56 Celsius as opposed to the 82 C it should be. This was before scanning for codes or anything. After I did a coolant flush last week, I noticed the temperature gauge was a little under where it used to be, but never realised it was a drop of 26 degrees. Good news on the gas mileage though! \:\!
 
Messages
25,046
Location
ON, Canada eh?
 Originally Posted By: Falcon_LS
Got it sorted! Believe it or not, it turned out the be the thermostat! Never would have imagined that being the cause...cheap replacement as well. \:\!
Good to hear! \:\! Why have a thermostat in your climate? Not like you need the heat in the passenger area! (J/K)
 
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