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1990 GT. 140K. Out to refresh the heads and head gaskets. Flipped it over on the engine stand to change the oil pan gasket and check the rod bearings.
This is what we found:
It's soft. It doesn't spring back (like rubber) when you squish it...it just flattens down and smears. Seems like carbon...but what would be the source?
I do know one thing....this engine was not far from having a completely restricted oil pick-up!
Some kind of Snake Oil Additive...and a lot of it over time?????
Cheers,
Dave
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David Roberts
2010 Jaguar XKR Coupe - 510HP Stock - Liquid Silver Metallic
928 Owners Club Co-Founder
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Maybe a lot of stop & go driving from many short commutes? This type of driving ends up making a lot of acids and water that is not vaporized by getting the engine up to operating temperature and that results in sludge.
I know you state that engine has 140K miles in a 90 GT, but what is the typical driving habit of the owner?
Sadly those who work on regular cars see such things all the time. Culprit is usually extended oil changes, cheap oil, short trips without warming up the car, failed A/O separator....any combination of those etc..
That is what sludge looks like.
Years ago when I purchased a 1999 SAAB 9-5, one owner car with 96k miles. Full records showing diligent oil changes.....first thing I did was drop the pan, it looked as bad as this 928. All the oil changes were at the dealer and I know this particular place liked to used refined oil and on top of that this engine was known for a breather system that could easily clog not allowing fresh air in.
Never ever use Motul oil. This is what happened to a BMW Alpina B10 4,6 V8, not once but twice. The very expensive oil Motul 300V Competetion 15W50 was used.
The car has always been used for long distance driving, no short trips, no additives, oil change intervals always within specs.
Åke
I had a similar problem when I put my 928 into storage, I drained the oil, probably a mistake, the oil was RoyalPurple, and about 6 years later there was just sludge mainly in the pan. I am rebuilding that engine now.
QUOTE=Strosek Ultra;15202197]
Never ever use Motul oil. This is what happened to a BMW Alpina B10 4,6 V8, not once but twice. The very expensive oil Motul 300V Competetion 15W50 was used.
The car has always been used for long distance driving, no short trips, no additives, oil change intervals always within specs.
Åke[/QUOTE]
If not, I wonder if this could result from shops that use vacuum system and don't use the drain plug, which doesn't completely empty the pan? Repeatedly not getting a good "drain" could result in sludge.
Sadly those who work on regular cars see such things all the time. Culprit is usually extended oil changes, cheap oil, short trips without warming up the car, failed A/O separator....any combination of those etc..
That is what sludge looks like.
Years ago when I purchased a 1999 SAAB 9-5, one owner car with 96k miles. Full records showing diligent oil changes.....first thing I did was drop the pan, it looked as bad as this 928. All the oil changes were at the dealer and I know this particular place liked to used refined oil and on top of that this engine was known for a breather system that could easily clog not allowing fresh air in.
Saab also took notice that the oil change interval was too long on the early 9-5’s. Dealers were unknowingly killing them slowly.
But that sludge is nasty. I have never seen anything that bad before, not even in any of my Saab’s.
08-08-2018, 10:40 PM
What is this stuff?
