Oil smells like gas.

[Kras]

OK, this has been bugging me for a little while.

Basically my oil smells like gas when I change it/check it.

My compression is within spec. I can tell my car runs rich (black smoke under heavy load, fuel smell from exhaust) but I get decent fuel economy(400+k per tank).

Is this a fairly normal problem for these cars?

I'm kind of leaning towards injectors not closing all the way and possibly washing out the cylinder walls a bit. Or maybe bad o2 sensors causing a rich condition?

Thoughts?

[nelsonmxmarc]

Typically happens when running rich or doing a lot of short-km trips. If you've got an AFR gauge handy that would narrow down your issue. My oil typically smells of gas; not harsh, but its definitely there. Just replaced my O2 as i was running a constant 13 AFR at 100 km/h.. Noticable difference now at a 14.9 avg.

EDIT - also tends to happen more in colder weather. Fuel Mixture is considerably richer.

[NismoS-tune]

Excess blowby, running too rich or low compression somewhere sometimes causes this. There's gotta be a point when the overfueling washes the cylinders. Something scary about running 11 AFR or less lol. No power either. MINE's runs theres at 13.7 or something no? steet gas?

[Skym]

Dry, wet compression test to check rings.

Check the PCV valve that should be located on intake manifold side of breather hose from intake manifold to intake camcover. They tend to block and cause excessive crankcase pressure. Sometimes need to be replaced or cleaned. Should only open one way, towards intake manifold under vacuum. Under boost, should be closed.

11.6:1 is considered to be a safe A/F ratio, 10.0:1 is rich.

When air is colder, MAF makes ECU hit the higher load cells on fuel, ignition maps. Fuel maps are richer at higher load cells. But stock GTR ECU could run richer, as stock GTR ECU has a IAT (Inlet Air Temp) sensor for intake temperature compensation.

[mcfly]

I agree with skym, do a leak down.

[GTR-Dad]

11.6:1 is considered to be a safe A/F ratio, 10.0:1 is rich.

Note to those running or planning to run more than about 1 bar, you'll want to watch EGT's to determine safe AFR. Depending on your cams, cam timing, and ignition timing, 11.6 may be on the lean side. Try to keep EGT below 900C with 950C as a 'do not exceed' number.

I think rich idle is more likely to result in cylinder wash than rich WOT. Ignition faults would probably be required to wash cylinders under load.

Dan

[NismoS-tune]

Ah, thanks for the clarification

[Kras]

Thanks for the responses guys. To clarify a few things, I am running the stock ECU and the car has been parked since the beginning of October so it hasn't really seen any cold weather driving.

I'm planning on buying an AFR gauge in the near future just to confirm that I am running as rich as I think I am. Until then I will check compression again I suppose.

[Skym]

Note to those running or planning to run more than about 1 bar, you'll want to watch EGT's to determine safe AFR. Depending on your cams, cam timing, and ignition timing, 11.6 may be on the lean side. Try to keep EGT below 900C with 950C as a 'do not exceed' number.

Good advice.

I'm talking about stock engine with stock cams, stock camgears, etc.

From what I understand, when boost is upped above 14.2psi with MAP setup, 11.0 A/F ratio might be better A/F ratio to use.

With aftermarket cams (depends on specs of cams), like you have said, run engine richer.

From what I understand camgears affects A/F ratio at certain rpm points, depending on how they are set.