 I have 3500 miles on this truck and im averaging 16 to 17 mpg in town and over 20 mpg on the highway with no mods except I use diesel kleen in the fuel. I do granny the throttle but with so much power you dont need to act like every time you accelerate its a 0-60 drag race.  Also I put 70psi cold pressure in my 20" stock tires and it seems to help a lot. But overall it's a great truck and I love. I also plan on putting a air intake system which should help even more.  