Originally posted by stilov:
have you been running pennzoil? It leaves a waxy sludge in the engine...Quaker state (I heard does something similar)



That hasn't been true for a long time, if indeed it was ever true. Pennzoil and Quaker State are hydrocracked oils, using Chevron's hydocracking process, as of several years ago. These are Group II basestocks--most of the 80cents/quart oils are still Group I.

To answer the original poster's question, I would suggest changing your oil with Shell Rotella Synthetic 5W-40. This is available at most Wal-Marts in gallon jugs. This oil is designed for both gasoline and diesel engines, and as such, has more detergents than gasoline-only engine oils, so it will clean out the deposits in your engine, and do it in a gradual and safe manner that won't result in plugging an oil passage.

Diesel engines put much more carbon and soot into the oil than gasoline engines, so that is why diesel engine oil has better detergents than gasoline oils.

I have used Shell Rotella oil to get rid of a lifter tick in my Mustang 5.0. In the case of the Contour, the 5W-40 weight won't hurt anything as I'm pretty sure that's what is specified in Europe.