Ive had 5 cummins trucks and most have gotten about 15-17mpg on average. My best ever was my '98 12valve Reg cab 2wd 5 speed. Very light for a diesel truck. I honestly averaged over 20 mpg most of the time, with 25 ish on long freeway trips. But, like i said, it probably weighed 1500 lbs less than the average truck, since most are 4x4 xcabs

I bought mine a couple of weeks ago. I drive 75 miles round trip daily. At 62 mph I am getting 24.5 mpg. I towed my 16ft trailer loaded at 6000lbs and got 21.5mpg. If I baby it it goes a little higher. In town it sucks literally, Im getting about 12 mpg in town. I have a 2008 dodge 2500 6.7 quad cab short box 4x4. thanks Rick

Is that all hand calculated?

exactly -- cause these new engines with the DPF on them are killing mileage -- all brands are having struggles with mileage on the newer models

I should Draft 18 wheelers and see what the MPG will be, i already know averaging 90+ will give ya 11 MPG

I have about 7000 miles on my 6.7 & I'm getting about 12mpg. I got 18mpg once before I put the 35's on it. I have no muffler & a S&B air intake set-up. When my wife drives it she gets about 16mpg regularly, but she isn't as heavy on the throttle as I am.

Yes, I filled it up, ran it four days for the exact miles. Then filled it up for the exact fuel used. then devided it. Then I done the same thing with towing my trailer. thanks Rick

Is everything stock on your truck?

I have a stock (for now) MegaCab DRW 4x4, 6.7 auto with 18,000 on her, had the turbo changed and all the latest updates, with high idel activated and.....love it. Towing around 7-8 tons, I average 10-10.2mpg at around 70mph. Unloaded, I average around 12.7 to 13 with my normal driving habits. If I grandpa it and never get over 2,000rpms...to include take off, up to 70 mph on the highway, I average 14.5mpg. All of this is hand calculated, I record every gallon of fuel that I put in any vehicle I own, personal or work. I can not for the life of me figure out how some of you guys are getting over 15mpg, maybe my computer is stuck in halla$$ mode, or maybe I need driving lessons to get over what I am averaging now. I have noticed that if I place it in tow/haul mode during take off, then switch back out after 60mph, I average better than if I don't do this, maybe eliminated some wasted power at the converter.

I'm getting about 17-19 around town, and have gotten as high as 26 on highway empty. I have found the overhead to be off about 2 or so mpg. I have found like largedakota said, that in tow haul i get much better mileage. Is it bad for the tranny to leave it in tow haul all the time? If it's not I might start doing that. I have an hour drive to and from work everyday, half interstate half 45-55 mph speeds.