[Garryese]

Towing I get 12-13 mpg. In town and highway combined with only the quads and sled on is 14 mpg. Highway with only quads and deck is 15-16 mpg. Highway empty is 16-17.5. Trying to conserve fuel on the highway I have gotten 17.6-17.9 consistantly. The best I got with a strong tail wind, only the sled deck, 108kmh is 18.8 mpg (boost stayed between 6 and 10 psi). The worse i got is 6.5mpg with sled deck, two quads, pulling my travel trailer into an 60kmh head wind while driving at 120kmh ( boost never dropped below 35 psi and 50% of the time it was dropped out of overdrive). My truck only sees WOT when passing and towing.

Mine is a Job 3 with factory ride height and tires/wheels, running 3.73 gearing, no chip or tuner. My truck is scaling in at 9000+ pounds full of fuel and sled deck on. I have 10000kms on mine.

For every 3 psi of boost you loose 1mpg
For every inch you lift the truck you loose 1mpg. This includes lifts and tires. Use a Job 2 or 3 air dam if you have a Job 1 to gain 2mpg.
Sled deck alone or a tonneau cover will increase milage by 1mpg.
Cetane booster works if fuel at the pumps is less than 43. BTW cetane at PetroPass's fluctuates greatly (35 to 43).
Regens cost you 2-3mpg for 10 to 30 minutes. Regens are avoided with high egt, but high egt are created with sustained high boost so it's a catch 22.

If milage is a concern or you idle alot forget any of the 08+ diesels, look for a low milage '07. Friends with 08 f350 all get worse milage than me, but all are lifted with 35-40" tires. Friends with '08 Cummins and Duramaxs all get the same or worse as me under similar circunstances.

F350 gas unit leaves you with only two options. No towing power in the V8 or 8-12 mpg all the time with the V10.

The Diesel Shop link Ron gave you has lots of info on milage, but also read about DPFs while your there. DPF delete kits with tuners are seeing 20-22 (some claiming 25) mpg in US gallons; Gains like this are worth killing the engine warrenty at some point.