i am stayin out of the octane wars forever! i will state a theory though. when any of my machines are running really well, i tend to really get heavy on the throttle(s) just 'cause it feels good. subsequently my milage will go down! runnin twisties like a mad man with 2 up tonight the VTX (black of course) got 50+ mpg. you'll have to guess the octane but i will say that chevron and shell seem to be consistantly good fuels.