[KevinH1990]

One of my neighbors is a chemist. He's retired now, but he previously worked for a company that made chemical additive packages for motor oil. One of his jobs was to perform destructive engine testing. Basically, they would add oil to an engine, run it, take it apart and measure wear on the various parts.

I've asked him a number of questions over the years about what kind of oil to use and how often to change it. His response has always been "follow the manufacurer's recommendation." Basically, if you change it too early or use synthetic when the manufacturer says non-synthertic is OK you are wasting money. His point is that the manufactures perform extensive testing on their engines and make their recommendations based on facts.

In response to the statement "I've always changed my oil at 3000 miles and never have a problem" he says, "If you had changed it at 6000 (or whatever the manufacturer requires) you wouldn't have a problem either. Think about this: With all the Boxster engine failures that we read about on this board, I don't think I've seen one attributed to oil failure or lack of lubrication from old oil.

Just for the record - I do use synthetic oil on one of my cars that doesn't require it because it does seem to slightly improve the gas mileage - although not enought to justify the higher cost. I also change the oil slightly more frequrently than the manufacturer requires. I drive my Boxster about 10k a year and change the oil every October.