Thin Oil

[TonyL]

I have a 1983 GMC with a 6.2L which seems to have very thin oil. I use 15W-40 oil and when drained even cold it is thinner than any warm oil I have ever seen. I am wondering about the posibilith of diesel fuel or coolant entering the oil. The oil is BLACK, not milkey or brown. I have done a compression test which shows about 33 psi in each cylinder. Any thoughts what i should check next would be greatly appreciated.

Thanks

Tony

[moondoggie]

Good Day!

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[TonyL]

THAT IS 330 PSI(TYPO. THE THING LEAKS SO DAMN MUCH OIL THAT I DONT NOTICE THE LEVEL RISING(I ADD A QUART EVERY 400 MILES) AND I USE NAPA OIL.

TONY

[Peter J. Bierman]

If your engine uses so much oil and has low compression it is probably fuel in your oil.
Normaly you must be able to smell it when taking a sniff at the oil. :rolleyes:

Time for a rebuild? :(

Peter

[moondoggie]

Good Day!

330 PSI doesn't sound like low compression to me (14.7 PSI atmospheric pressure x 21.3/1 compression ratio ≈ 313 PSI). Hopefully others will add more competent feedback.

Blessings!

Brian Johnson, #5044

[DonG]

TonyL,

One way to check for diesel in your oil is to drip several representative drops onto a paper towel. If two rings form then that is bad. One ring for oil, the other for diesel. You may need to try this several times to make sure you have a representative sample.

Good Luck, Don

[TonyL]

how could diesel fuel enter the oil besides going past the rins in the cylinder?

[EWC]

Bad seal in injection pump ??

[britannic]

Originally posted by EWC:
Bad seal in injection pump ?? I agree, fuel could get past a bad seal and down the IP driveshaft into the timing chest. The other possibility is the lift pump (mechanical), if the diaphragm fails, fuel will enter the block gallery and thence straight into the oil pan.

[gmctd]

Inj pump has two seals to keep fuel from oil and one additional seal to keep oil from fuel, but that is a distinct possibility.

Also extended idling periods, where fuel can wash oil from cylinder walls, increasing wear.

Black color is soot from combustion process - this stuf will eat cam, main and rod bearings - worn engine requires more frequent oil\filter changes.

City-driven engines will evidence more soot than hiway-driven engines.

[eracers999]

Tony;
The lift pump on your 83 6.2 would will be the most likly source of fuel in the oil.
Just trying to help.


Kent