Whoops, I can't subtract. That would a difference of 6 not 8 octane.

No he is just wasting his money.

Actually the higher octane will run cooler. More likely to cause carbon buildup. A waste of money.

When I bought my (Stihl) chainsaw a few years ago, the tech told me to use premium because it contains less ethanol than 87/regular.

I haven't had time to confirm if that statement is true.
That said, the saw and everything else I run on super, works great.

Other than that, unless you're running a high compression engine, the extra octane is a complete waste of money.

An't gong to matter! running the engine with the air filter removed will alow all the dust, grass clippings, to be sucked down the carb. If that don't plug the carb. up it will soon wear the piston to cylinder wall clearance, turn the oil to gritty past and it will start smoking, knocking, and eventually won't start. If he really wants to save money and heartaches down the road spend the extra money he is wasting on high octane gas on a new air filter. That would be the best bang for his buck if it an't too late???????????????????????????????????????????????????????????????