2009 dodge 3500 dually, auto full slt package. 6.7 Cummins. 70,000 miles . Presently was getting at best 19.1 mph driving 60 to 65 mph no load. Installed a Delete kit and exhaust system with live wire 5 stage switch and programmer. In 1 setting g I now get documented 25.8 mph on same driving . In tow mode pulling7500 lb fifth wheel 11.9 mpg all day. Truck is totally stock except for programmer. FYI I worked in major dealer shops, Diesel ASE certified master tech. GM tech for 10 of them years working in truck department. Dealers are so full of crap. They try to scare the public into thinking your programmer caused your problem. In most every case I have ever seen unless you dog the crap out of your vehicle, programmers are fine. As with any piece of equipment you have to assume a responsibility that if your vehicle breaks the dealer cries foul. They will try and find anything and excuse to not pay for a repair. Sorry to say most valve drops or engine failure is do to defect. Look at race cars. Good example. Serious about programmers do your research first and ask yourself is this worth the expense if it goes haywire.