+1 on BlackBurns post. Run at least 89. It will make a night and day difference if you try to go back to 87. I didn't realize the difference until I tried going back to 87 (after 2 months of 89). Now I'm stuck with a tank of crap gas. My milage increase covers the additional cost going from 87 to 89 so I don't think i will ever intentionally put 87 in my car again.