^ You make no sense. Top tier gas is not an elusive thing. It's at most gas stations these days.
Higher octane is just overpaying for something with no benefit, unless you have carbon buildup and are drag racing your mower? lol.
You need to step back and consider what others have had success doing, without wasting money on myths. If you have FACTS to the contrary, I mean based on observed issues with your engine, then that's a start and I can get more specific with mine that has no such burdens, but it is only 22 years old, you might have some dinosaur that has special needs, but one of them is not likely to be 90 octane gas for a B&S engine, lol.