I tend to go with the highest octane available without ethanol. We were in Iowa a couple weeks ago, and I needed gas, so, I filled up with their best non-ethanol grade. The bike ran like CRAP until I could get a tank of good gas back in it. Maybe I got the bottom of the barrel.....That gas was only rated 87 octane/ethanol free...that seemed a little weird to me. They also had it labeled "recreational use". When gas in WI is labeled recreational use, it's typically the best ethanol free stuff they got, and it usually works great in the Spyder. I'm guessing that the bike "learns" what kind of gas it's burning after so many miles and makes the proper adjustments. In my case that day, going from premium to crap.....it kicked the bike right in the cahoonies and it fell on its face. So, burn what you like, but I think it's best to stick to that grade and not jump back and forth between grades to save few cents now and then