I average 16-17 running at 65 interstate driving with 3.73 gears truck is 8,000+. Around where I live which is some what rural I get 12-14 Last weekend I drove 250 miles interstate and burning winter diesel I got exactly 16 MPG. All figures were driving empty.

 

I had a 2006 f250 4x4 and bully dog chip, got around 20mpg on highway and 17 towing my boat, traded it in for 2009 F250 4x4 and only get 15 on the highway, no tuner, I believe the truck could get alot better mpg, just havent found the right tuner or exhaust to put on it,

 

From what I've seen on this and some other sites the Spartan tuner and DPF delete kit is the way to go to improve fuel efficiency and get rid of regenerations. I don't have first hand experience because for what I use a truck for diesel is cost prohibitive. I could never get more than 16.5 mpg on my 05 6.0L empty highway or 11 mpg towing my 20' enclosed car hauler.