Scott Crumpton
Ethanol free gas or aviation fuel if you can get it. Otherwise, 93 octane does seem to work better than regular. If the gas station has one of those pumps with only one hose and you select the grade, put the first 2 gallons in your car and the last one in the fuel container. The hose will contain a gallon or two of what ever the last customer pumped, probably the cheep stuff.

Slightly OT, but learn how to tune the saw and tune it to run on the rich side. Most come tuned too lean due to EPA regs and is a major cause of failures. You may need to remove the limiter caps from the needle valves. Also, opening up the muffler for butter exhaust flow (and retuning) can significantly improve power. There's a lot of information available on the various arborist forums.