When my dad was looking at a truck, he took a good hard look at my NA IDI F250. I was getting GREAT milage 25 Miles per imperial gallon (21 MPG U.S.) out of it. This is when he decided he wanted a 3/4 ton or 1 ton SRW diesel.
The truck he bought, was a 1999 Dodge Ram 2500 24v, Auto, 4x4 ext cab. short box.. It had 245/75R16's on it, but he has since put 265/75R16's on. Changing the tire size did nothing for his milage, and it still sucks on fuel!
I am not knocking on Cummins, as I drive an N14 Celect Plus and i love it, but I thought that it would get better than 15 miles per imparial gallon (or 12 MPG U.S.)!!!!
I don't know if there is a problem with it now, but the wastegate was stuck. We freed that up and gained 1 MPG out of it, but that was it!
It had new injectors, a new lift pump and a new turbo installed about a year ago, just before he bought it.
Tough as nails though, just not very efficient lol.