I got an 04 F-350, crew cab and dual axles.
Job box in the back adds another 500#. Im getting 12.3-12.5 mpg on diesel.
My buddy has a 250 with the 7.0 diesel, crew cab, and gets 14 mpg taking it easy on it.
I would have a van/sprinter except I also need to transport the kids around town. Before this truck, I had 3500 gmc gas engine with an ARE contractor cap, which I really liked( the cap ). This big block truck averaged 8-10 mpg. Sucked gas and hauled ass.