Metro, I know! I was using opening all the windows as an air brake - when you roll down all 4 windows that little bucket catches quite a bit of air - didn't hurt that it was pretty hot and that helped cool us down.
I think I need a Transformer(tm).
Hypermileatron?!
Maybe the truly advanced hypermiler who has power brakes can set up retractable air brakes? Make the sunroof open straight up?
I doubt Michael Bay is going to include Hypermileatron in Transformers 2, but we can dream . . .