I heard there was less ethanol in premium . How true that is, I don't really know. I always ran the highest octane I could get, as this makes the fuel more stabil, causing a more even and slower burn rate, which will help with preiginition. The lower the octane, the less stable or faster the fuel burns. So if your fuel burns to quick, before the piston gets to top dead center, you are trying to force the piston back down , the opposite way it's turning, thus , this causes alot of wear on your lower end bearings as well as the piston, etc. If you get no pinging , you should be fine. I learned this thru going to Harley Davidson school, when I worked as a Harley Tech for a local dealer years ago. By the way, that seafoam will speak for itself. You'll see. Your stuff will always start and run fine . You'll never not use it, once you see for yourself. I had stuff sit with that in, that I thought would never start, and started. By the way, Seafoam will stabilize gas for up to 2 years.