High octane fuels are for High compression vehicles only. I have encountered the myth about fuel economy many times, the differance high octane fuel provide in fuel economy (if any) is more than offset by the higher price. I do suggest blown or other high compression vehicles to use a higher octane level but going over 100 is unnessesary for any registered, street legal vehicle. My two cents are in, mind you they are canadian cents so they are not worth as much down there in the states
john
custom cars are supposed to have bigger engines than stereos, but maybe i'm old fashioned.