In my area we have good availability of ethanol-free gasoline. The few stations that have premium (93 octane) are disappearing. There seems to be a trend to carry only mid-grade (90 octane). The Rotax manual for the 912 ULS states that minimum of 91 octane fuel should be used. There are octane boosters, from auto parts stores, that can be added to the fuel to raise the octane by as much as 3 numbers. Anyone have any comments, knowledge, or info on this topic? Thanks Gary