Unless you're mowing acres, the few pennies shouldn't make a difference, doubt mid grade would hurt it and if your manual says "minimum."

I put in Stabil (That's a fuel stabilizer, several different ones out there, purpose is to offset the adverse issues of ethanol in gas) everytime I fill one of the small engine gas cans, SeaFoam I put in occassionally just for cleaning. Don't know if SeaFoam is a stabilizer as well as a cleaner?

I do the same thing always use fuel stabilizer n yes sea foam is a stabilizer. I was surprised when he told me my carb was gummed up.

Lot of people work on lawnmowers, myself included, doesn't make me an expert. I'd suggest getting another shop, no one sane would say not to use stabilizer with today's fuel in small engines. The only fuel upgrade I'm aware of in small engines is Stihl two cycles reccomend mid grade. JMHO

Ev