Just made a trip from Houston Texas to Illinois. 2012 Crew Cab Lonestar. 3.55 gears, with all the performance mods listed in my sig.
I made it all the way from Houston to Nueton Illinois on a tank and a half of gas. So 1 1/2 tanks in the smaller tank size. I TURN MDS OFF, and averaged 22mpg at 80-85mpg cruise control set. IMO MDS IS A GIMIC. Just makes useless crappy drone and Honda Civic noises and does not EVER net me a difference in MPG. Not to mention hearing it kick in and on constantly along with feeling it do said kicking on and off nets a VERY uncomfortable ride.
There has got to be something you are leaving out. I could not understand how you are only getting 9mpg, and there not be a HUGE problem that is easy to spot and fix. I mean I drive the living bat crap out of my truck. I drive it HARD a lot. I mean I have caught some of the local PD in their Fords and Chevys, on the back roads leading to the freeway where I live, still in uniform getting off of their shift and we always go at it. Never do I do it on an open road with another person in the truck and others on the road yada yada yada. I still get average of at least 12mpg. That is VERY weird. Let us know what you find out and the fix (if it ever gets fixed) and if you run into dealer problems get a hold of the local rep and go to a different dealership. All dealerships have to recognize your warranty NOT just the one you bought it from.
Good luck friend!