Hey Guys,
Don't know if this is much help, but here in Oz, since about 100 of my 1000+ Customers are running Fords, I have been experiementing with an F-250 and my new CC 4x4 F-350 King Ranch 6.0 Auto FX4 LWB Dually....
And have some mileage results, from Stock to different levels from 1 removing some emission controls to level 5 Race....
Now running a simple tuner, Edge Juice with Attitude Module, Cat Gut, Dually gets 15.95
measured and calculated on highway stock at 2000 rpm and 17.38 mpg on Higher level 5.... But I weigh about a ton extra with equipment on board, so that is pretty good
Around town, there seems to be a better mileage picture as well, but only if you use the added torque to shift early, taking your foot off to shift early, and you run on torque more than rpm... Around town this boosts mileage as well.. Level 5 is 100 hp over stock, and if you keep your foot out of it (hard, very hard with some itchy-gootchie passing you) if you run light footed the torque seems to carry you shifting at lower rpm...
Hope this is a help.. works for me here in Oz... (Australia)
Kind Regards from the lone Ranger, out on the last Frontier