I have a 2007 DuraMax automatic...bought it used in 2012 and the first thing I did after replacing the windshield was have a Super Chip put in. Before I was lucky to get 13 mpg on the highway and even less in traffic. This is a HD 3500 Sierra crew cab. Now the mileage in the performance mode is between 14 and 20.2 mpg on open road depending on traffic. I pull a 3 horse gooseneck L/Q trailer that's 41' and with the truck I'm 58' and with 2 horses. In the towing mode pulling the trailer on open road, not too many hills, in east Texas I get 9.0 to 12.1 again depending on traffic. I really like my truck and have always been a Dodge ram fan, but I was tired of shifting and my 96 250 was so rough unless the bed was loaded, plus it wasn't made to haul 19,000 gvw trailer. So thumbs up on the Super Chip...
