What could cause the engine oil turned to sludge in an 2004 Pontiac Grand Prix?

Asked by Jan 06, 2016 at 02:14 PM about the 2004 Pontiac Grand Prix GTP

Question type: General

I change the oil in my Grand Prix GTP regularly.  When I took the oil plug out no oil came out of my car.  Then I took the Oil Filter off and I could not see the threads on the oil filter and there was a sludge all over the top of it.  I left the oil plug out all night to drain and all that came out was the same sludge that was on the oil filter.

5 Answers


Something does not add up. If you change the oil every 3-4,000 miles then there is no way the oil could turn to sludge and not drain out. Your engine would be seized up or have a major rod knock. What does the sludge look like?

I have attached another picture that shows how thick the sludge is. It comes out in globs.


I would check the head gasket, it might be bad, This is probably a good place to check as the 3800 are known to have bad head gaskets, This means that coolant is mixing with your oil causing the slug like oil, I would start with the head gasket and move on from there since most oil problems with slug involve head gasket problems

1 of 1 people found this helpful.

I sort of agree with the coolant in the oil theory except the sludge should really be a milky color, not black. It looks more like oil that has never been changed, but I'm assuming that is not the case. Is there anything else it may have been contaminated with? Is the car running OK otherwise?


That sludge looks like 200,000 miles with no oil changes. Did someone put several quarts of tar in your engine?

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