Tsb: 01-06-01-281 issued 3/2003
Describes it as you say. In a nut shell the article that GM put out says don't worry about it won't hurt anything. It is caused by the formation and of carbon on the piston and interaction of the piston, cylinderwalls and the motions of them.
You can try using GM top cleaner or seafoam to help break down the carbon, but it may not.
Synthetic oil is fine. The problem is that the filters don't last as long as the oil. If you change your oil 3000 or 3 months with normal 5w30 oil you'll be fine and save $.
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Wednesday, January 10th, 2007 AT 8:09 PM