premium. For better or worse, I'm mapped for nothing but 93. Even 93 with 10% ethanol causes my car to run a touch leaner, and on hotter days, the car will ping. Normally it pings just a bit, but if I try to run anything less than 93, it detonates hard. I learned my lesson after blowing head gaskets, breaking ring lands, and bending two rods in the worst case. Most of the time on ethanol'd gas, it usually just detonates hard enough to break a spark plug or two.