0 - 3,000 miles: I used whatever came in the engine from the factory
3,000 - 15,000 miles: I used Red Line 5W-30 Synthetic. My only complaint was that I had to special order it because I couldn't find it anywhere locally and it was sort of expensive, but other than that, I thought it was a very good oil.
15,000 - 28,000 miles (approximate mileage as of 1/2009): I've been using Royal Purple 5W-30 Synthetic. Honestly, I didn't notice any difference in performance when I switched from Red Line to Royal Purple. I'm just happy that I can find it locally and it's slightly less expensive than Red Line. I think you'll be happy with it too.