Rabbit, I sell programmers of several different brands and from the feedback I have gotten from customers is the Bully Dog is by far the best. I run one on my 01 7.3 powerstroke, with 40" tires I still get about 16 mpg, also have one on our 08 6.4 and it picked up about 4 mpg over what it got stock. I get about 12 mpg with the 08 pulling a 28' enclosed and 70-80 mph towing.