[SD987]

Perhaps I wasn't clear enough. Actually, as I said, Porsche DOES gain by recommending a longer interval, as it lowers the perceived cost-to-own (maintenance costs) of their cars in the eyes of potential buyers, thus making them more marketable and competitive.

You were clear (but thanks for using small words), however you're overestimating the marketing benefit of the oil-change interval.

I can think of few automobile purchases more impractical than a convertible two-seater, particularly one costing 50-70k. If you were talking a family-toter perhaps, but I suspect the number of 987 buyers whose purchase decision was influenced by a 20k service interval = 0. Especially, since the majority of car buyers don't even crack open the service manual until after the purchase.

As I mentioned before, your theory also doesn't shed any light on why Porsche picked 20k. The marketing benefit could have been achieved by selecting 16k, or 17.5k, and yet they made it 20k. Think the marketing guys said, "hey, let's go with 20k cuz it sounds like alot"? Perhaps, perhaps not. As I said, I suspect 20k is actually understated.

But echoing the obvious point made by Bruce, to each his own. If you want to go with short oil change intervals because, Bob the oil can guy's website says so, or because your uncle Gus maintained his car like that and swore by it, than go for it ! It's your car, your money. If I want to believe that Porsche and Mobil one's engineers think 20k is the appropriate interval for a 3.2 liter engine with 10 quarts of synthetic oil, I fully accept the consequences. I don't think either group is going to convince the other.