The worst mpg I ever saw in mine was 14.5 and that was when I had a caliper hanging on the front. The truck stock on 295/75 tire got 17.5, went to 35" tires, added an edge comp and 100hp injector and I average 18-19 and it's all local. I hauled a 5500 pound ram on a 2000 pounds trailer through the ridges/mountains recently and still got 16 plus on that 200 mile trip.

If your going to haul a trailer even a few thousand miles a year, to me a cummins is well worth it. When you live where it's all hills like I do, it'd be hard to even consider anything less for towing.