Redline 10W-30 - but don't go for the super-long intervals (they recommend 10-18K miles), I went 9300 miles last time and sent it in for oil analysis - the total base number (measure of alkalinity, ability to neutralize acid) was way down, and the lead levels were rather high. I am trying it again with 5K interval.

BTW - all you Mobil1 and Castrol syntec fans - you are aware that they aren't 100% true synthetic, right? Castrol is a super-cracked crude oil, and Mobil1 has a crude-based component (at least the tri-synthetic formula did - not sure about the newer super-syn, but since the price didn't go up, I assume it has not changed that much.) Both are a step up from crude based oil, but not as good as premium synthetics such as Redline and Amsoil.