Mileage has to do with many factors. Driving habits. Vehicle weight. Rear gear ratio. Engine tuning. Tire pressure and size. The "magic" turbo-plates and mythological "500 mpg." carburetor are all part of marketing in America. OPTIMIMUM Mileage is acquired by modern technology in fuel delivery(port injection) and ignition (electronic computer controlled) combined with good driving habits, not necessarily the madness of hypermiling.