I run 93 octane. But 91 is also acceptable. Anything higher than 93 (ie, CAM2 racing fuel) and you are just waisting your money. It will not give you any better performance. The ECU has the fuel scheduling setup to be efficient with 91. Anything less than 91 and you will probably experience "pinging" (predetonation) that can, and will, damage your pistons and valves.