Those are scams. They do absolutely nothing but lighten your wallet. The only way to save gas is slow down. That and easy acceleration. It's easy to get a V10 to go from 9 to 14 mpg, just let off the throttle a hair (75 instead of 78 mph, for example). There are too many unknowns to say it increased mileage that much.
Last edited by Raptor05121; 05-19-2008 at 10:40 AM.