I have been thining of what is the best gas for my outboard. The tag says to use gas with 89 octane rating. Mixed at 50/1 Locally I can get 3 grades of fuel. Reg. 87 mid grade 89 premium 92 to 93. My question comes up from checking out the way fuels sell. The fast seller is 87. The next is the premium. The slowest seller at a station is the mid grade 89 octane. I have always heard that fuel will loose octane sitting. If the mid grade moves the slowest than how much loss has there been? My thoughts are would you be better off mixing the 87 & 92 octane so that you would have a fresher fuel? Cost would average out about the same. What are others oppions?