Well, I just sold my Shadow and bought a 919. The compression ratio is 10.8:1, which while not high for a sport bike, I thought was still high in the general scheme of things. So, I'm reading the manual and it recomends 86 octane and above. Now, as far as I'm concerned that's really cool. I was very convinced I would have to burn 91 or 92. But why so low? My Shadow had the same recomendation and it was 9:1.