said by supergas :I don't know where you are but here all grades are labeled 10 percent but that varies all over the place from 5 percent to 20 percent. The 20 percent is causing all kinds of grief to those buying it.
I too doubt the mower cares about the octane but, at least around here super/premium/hi-octane is ethanol free. While regular and mid grade "may contain up-to 10% ethanol." That's the only reason I use it in my mower and trimmer. I'd like to think by now small engine manufactures have learned to deal with ethanol but it's cheap insurance.