WOW, I dont know how one can just ignore the oil changes for 50k miles! The sludge could be removed but you might as well buy the car cheap and rebuild the engine so evereything in the engine is brand spaking new with no dirt to worry about. Even though you might be able to remove the sludge, there will still be some left over and over time, will break loose and cause another critical engine part to fail.

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2001 E55

2001 E320 Sedan

2001 Subaru Legacy

2006 SLK280

2016 Subaru Outback 3.6