DEF is a good point Vash. 2013 and prior get HORRID fuel mileage as u say. Starting in 2014 with DEF it's a different story. Not towing, I can easily get 21MPG on the highway and 18.5 around town (my old POS Honda CRV only used to get 23-24 ....). Towing 20K I get 12.4 MPG consistently (several trips Michigan to Florida). DEF fluid is cheap and I only have to fill it every few months at most.
Denis - I bought the truck at auction (clean service history) 2 years ago. It had been a contractor's truck and was setup for a gooseneck trailer. So I assume many of the miles are towing. I've had one problem - towing the 20K trailer up the steepest section of I-75 in Tennessee I suddenly heard a loud POP and lost at least 50% power
Scared the **** out of me because there are no shoulders on that steep, winding section to pull over and I was running with a bunch of semis. Long story short, I nursed it to a RAM dealer 40 miles away (all on steep grades) thinking I blew a turbo. I could only do about 50MPH. Mechanic found a turbo hose that somebody had screwed around with previously and was not clamped right.