I'm getting 11.5, with a trailer, empty or full. Sounds awful but in reality is as good as my 08 lmm dmax; especially considering this truck is geared 4.30, has 19.5's, and weighs in with driver and full of fuel at 10,300lbs.
Mods are- h&s mini Maxx, deleted pipes and egr, s&b intake, cold air charge tube, Rudy's up pipes, new/rebuilt pumps/turbos/coolers/injectors and other accessories. Turns 2250 rpm @ 70 mph empty or loaded. Haven't run a tank out yet w/out trailer to get an unladen/no trailer mpg.
For comparison the chevy mods are- h&s mini Maxx, deleted egr and filter, factory air box, geared 3.73, 225/70-17 tires and weighs in at around 8200lbs. On a good day towing it gets 11.5-12.5 turning 1950rpm at 70 mph loaded. Unladen without trailer, best tank mpg has been 17.5.
If anyone's interested I'll give my ford/Chevy towing comparison. That will take a few pages. ..