Gas in engine oil

[Jason43]

Several weeks ago I had sporadic warning lights come on including the MIL, yet no codes could be retrieved. I decided to change the auxiliary battery since it was 4 years old and the car has 123,000 miles, and that seemed to fix the problem. Right after this I changed the oil and was surprised to find the strong smell of gas which was so heavy that I could see the vapors coming off the hot oil. I was a bit alarmed and checked the plugs for fouling and they looked fine. I checked the fuel pressure and it was normal at 45psi. Since then I have checked the oil and it does not seem to be contaminated with fuel anymore.

Does anyone have any idea what happened here, and do I have anything to worry about?

[Patrick Wong]

Hi Jason,

If you had the check engine light on, then it is guaranteed that DTC were logged. However a generic OBD-II code reader might or might not retrieve the codes. This is because many Prius ECUs can log DTC and a generic code reader will be confused. Should this happen again, you'll need to visit a Toyota dealer to have the DTC retrieved.

Regarding the smell of gasoline in the oil, how many miles did you drive before replacing the oil?

Regarding your observation that you could see vapor coming off the hot oil, is it possible that this is water condensation that is evaporating?

If you don't see contamination in the freshly changed oil after driving 1,000 miles, the spark plugs are normal, and you don't see visible exhaust emissions, then I wouldn't worry about that.

[Jason43]

Patrick,

I have the scangaugeII and the DTC was P0000 which I guess means that no code was stored. I change the oil every 3k. The vapor was definitely gasoline and not water.

[Patrick Wong]

Hi Jason,

ScanGauge is known to not be able to retrieve Prius-specific DTC. After all, it is a generic device intended for use with almost all vehicles.

Regarding your observation of gasoline in the oil, if your driving pattern prior to the oil change consisted of many short trips, then it is possible that unburnt gasoline might accumulate in the oil. In that case, it is good that you change the oil at 3K mile intervals.

[tochatihu]

Some Prius engine oil analyses show about 1% fuel dilution, which is high. Sampling engine oil after the engine has been run but is still somewhat cold can certainly contribute, but the picture with Prius is still unclear (at least in my mind). A longish drive should certainly 'burn off' the fuel dilution if enverything else is working correctly.

Replacing th PCV valve might help. You sound like a handy guy, checking fuel pressure and all, so why not try that?

Step 1 is remove winshield wipers. No kidding.

[Spartane]

Originally Posted by Patrick Wong

ScanGauge is known to not be able to retrieve Prius-specific DTC. After all, it is a generic device intended for use with almost all vehicles.

Hi Patrick,

Do you know of a ScanGauge alternative that might be more Prius-specific (e.g.) maybe a laptop solution of some sort?

[jdenenberg]

Originally Posted by Spartane

Do you know of a ScanGauge alternative that might be more Prius-specific (e.g.) maybe a laptop solution of some sort?

I'm not Pat but there is: AutoEnginuity® - OBD2 Scan Tool - Professional PC and PDA Diagnostics which is available with Toyota code software for about $450.

JeffD

[Spartane]

Originally Posted by jdenenberg

I'm not Pat but there is: AutoEnginuity® - OBD2 Scan Tool - Professional PC and PDA Diagnostics which is available with Toyota code software for about $450.

JeffD

Thanks Jeff.