I do 75 mph and I've seen absolutely zero savings between what I drive and the double nickel - I tried it for a week and it totally SUCKED.
Maybe if I drove some small off-shore compact auto created with the ectomorphic in mind they'd be a noticeable difference.
But I don't so therefore there ain't.
Ponder this all you cerebral types; If there is really is a petroleum shortage why does NASCAR exist?
d'oh!