i drove my 06 2500HD with the 8.1 liter from ohio to florida yesterday. it only used a tank and a half. thats awesome! i installed a tornado fuel saver were the hose attaches to the throttle body instead of at the filter. i calculated it to be getting about 18 mpg, which is better than the 14 i was expecting. i will also be posting some new pics of the truck later on today.