[SV650rules]

There is less of the stuff that burns in higher octane but spark timing is the key to getting it to burn in a more controlled and efficient way inside the engine. If knock detectors are fitted and they detect knocking they retard ignition to stop knocking which reduces engine power. By clever design of combustion chamber and maybe twin spark plugs to 'light the fire in two places at once' higher compression ratios can be used on normal octane fuel, but an engine fitted with knock sensors and proper maps in ECU can make use of a range of octane ratings, and some can get good results on better fuel.

The formulation of petrol changes between winter and summer anyway, it is made more volatile in winter to make evaporation at lower temperatures better.