I've got 6.7 2500 auto, buddy has 6.7 3500 manual dually. After the warranty ran dry I deleted the DPF, egr, put on a programmer and cold air intake. I get 18.5 or so on the highway buddy has about the same mods and gets about the same mileage. Before mods I got 13. Pulling a load is 13 or less. I put all mods on after warranty and at the same time so I don't know what helped the most.
i got 5yrs or 100,000 bumper to bumper warrenty, so its gonna b a while before i yank exhaust out, again unless no honor on warrenty, no can do. i will just have to deal with it till warrenty is up. i just got rid of my 06 5.9 with some mods, pushing close to 600hp and when i took big tires off, i went from 12-13 up to 15-17. i still had the lift, but before the lift and tires, i was getting 22-24 hwy and 18 city. im kinda kickn my self in the butt for trading it in on this new junk, but thhe rear end was about to grenade on me
