Rode my 06 RK for two month before I bought an Owners manual. I used 87 octane gas until I read in the manual that 91 was recommended. The station carried 87, 89, and 93 octane. I noticed a big difference in sound and performance with the first tank of 93 octane.
Premium 93 if possible,I havent tried it in my SGS but I have mixed aviation gas in with previous bikes and or Turbo Blue race gasoline. Smells great burns cleaner, I drag raced cars for years so I was familiar with race fuel. However expensive and to really get full potential you have to tune for it.