One theory I heard from the local lawnmower guru - the alcohol fuel burns hotter, and so he recommends going up a notch on octane, which typically translates to using mid grade if the unit calls for regular. He believes the mid grade will burn cooler than the regular.
On the other hand, he suggested if my mower (bought used) was used to conventional oil, then don't change over to synthetic. I can't allow as how I'd agree with that, but I could be wrong. I typically try to mow when it's the coolest parts of the day, so oil breakdown due to high temps likely wouldn't warrant synthetic anyway.
I've been taking his advice on the mid grade, but I wonder what a proper engineer would have to say on the subject?
