What David said except personally I've had good luck burning E10 in all my 2C engines. HOWEVER none of them are aircraft engines. Just chain saws, trimmers etc. My saws can set for 6 to 8 months between use and the seem to run just fine. YMMV. OH, As a former Stihl tech, yes I'm biased, I feel the Stihl Ultra oil is in the top three. IMO it is #1 but arguing the difference at this level is a waste of time. I like it is readily available. I also run all my engines at a 40:1 ratio and do not have carbon issues.

Ken