Grudgingly, I use 93 Octane, since I can't find any "real fuel" that's not racing fuel at $10 a gallon. How I miss Sunoco 260 at the regular pumps for a few cents more...
That brings back memories of when I was 16 and liked hot rod cars!
I fill up with Premium (91). This is the first time I've actually followed the recommended octane. I figured it's only a couple extra cents per fill up and I want the bike to last me a long time.
Rode my bike 200 miles, filled it up with 87 because it didn't come with an owners manual. I bought the manual and read the 91+. It will be 91+ from now on. Not that much difference in price. It beats putting it into the car.
The compression ratio sets the spec for octane.
I use regular fuel SP95 ('95RON' = 91 in the US) because our SP98 tends to diffuse through rubber tubes and seals leaving a typical smell