Just google fuel saving devices,they are all a scam,some even loose mileage.if you want to save fuel,keep your motor tuned up,air in your tires,dont take off from a start as if you are going to a race,you dont have to run your rpms to the max before shifting gears.There are so many things that in changing your driving habbits,that can increase your fuel mileage,and save you significant money every month.Best way to save money,give your drivers a % of the savings.In just slowing the truck down,not only will save fuel,will also make your tires last longer,fan belts last longer,oil change at longer intervals.Cat recomends changing your oil at 2500 gallons of fuel,in a years time,changing your oil 1 less time doesnt seem like much,but in the high cost of operation in todays world,every dime saved is a big help