I am very happy with my mileage numbers after reading all these posts! My impression is that the Cummins do tend to do a bit better on mileage depending on variables of course.
Maybe it's the two fewer cylinders?
Anyway, I can get consistent 19 mpg unloaded (hand calculated, lie-o-meter shows about 20). On my recent trip to pick up the Monty in OK. I averaged right around 19.2 and a LOT of 75 mph running across I-40.
My truck is not stock (power and efficiency ehancements) and is geared pretty high. 3.73 gears but with 34.5" tires give me an effective ratio of around 3.55.
At 65 mph, I am only turning 1,650 rpm, really in the "sweet spot".
The truck loves to cruise at 75, still only turning around 1,750-1,800.
Very hard to tow at 55 mph, the engine is just turning too slow and the EGTs tend to run high unless I take it out of O.D.
After the return trip with the new trailer, I had just over 13 mpg over 1,550 miles with the trailer. Some headwinds too and this was a lot of 60-65 mph towing.
Sorry guys, really not trying to rub it in...one reason I went with the '06 Cummins- no DPF and better mileage from what I had heard. So far so good...
