93 In my GSR, because it says so on the cluster and on the filler door. I've heard they run like crap off of 87 octane, but I haven't been willing to test that theory. Not quite sure why it's that way though. Anyway, I run 87 octane in everything else in my driveway. I've tried switching to 89 in my sunfire, but never noticed a difference. Since I'm a cheapa$$, I switched back to 87