I buy & mix no-E gas and Stihl’s HP Ultra 5 gallons at a time, 50:1 manufacturers suggested ratio. Though I put the German oil in the Swedish saws, don’t tell any one. Soon I will have the first XP sold by my shop to crack 1,000 hours on it.
When I near the end of a job and will be switching to a non-saw job for a while I buy one gallon at a time. Whatever small portion of the one gallon is left I keep till the next saw job. In between saw jobs, when I might run into a downed tree on the way home from backwoods Brook Trout hunting, I keep a can of one of the big 2’s pre-mix in the tool box instead of the one gallon can. When saw work starts up again I simply mix whatever is left from the pre-mix and the one gallon can and then buy a 5 gallon can full.
I like the idea of using Amsoil in my saws but will stick with the HP Ultra. I’m not into racing things or continually trying to re-engineer whatever a manufacturer does, for the most part. But I do run Amsoil in my truck though, which has 560,000 miles on it and just invested in a new set of fuel injectors for it as the rods are strong in the ‘00 7.3 and it is now just nicely broken in.
I absolutely will not breathe in AvGas saw exhaust however, even when working with a friend who buys it by the 55 gallon barrel and offers it to me free.