Octane ratings dictate the basic property in fuel that makes them resistant to pre-ignition the result of which is detonation. Without getting into brain swelling tech info, the fuel burns slower. The result is less knock ( which the computer listens for to determine engine timing) and increased performance due to allowable increase in ign timing etc. In the old days of hi compression, hi octane leaded fuel reduced knock on Hi Comp engines, but these engines had inefficient cylnder head designs and limited ignition timing control, not to mention limited ability to mix fuel/air efficiently of the broad range of operating characteristics (load, eng speed etc). Remember the 08 accord uses 10.5:1 compression now
