I'm sure the dealer would rather have you buy 10w60 from them at $10/qt instead of 5w30 synthetic anywhere at $3-4/qt. As I understand it, a piston ring change early 00 allows the engine to run the lighter oil without burning it. My 02 stopped burning oil around 8-10k miles and I've only used the 5w30, just like the manual and sticker under the hood recommend.