That's a pretty open ended question with all the different engine / gearing options. For example, a 3.55 runs about 15% more RPM's on the highway than my 3.31, for exactly the same speed, but that doesn't translate to 15% less fuel used, because the 3.31 has less torque b/c of less RPM's, and uses more boost. From what I can see, 400 rpm's = a 2 lb. reduction in boost, give or take.
Also, my '16 weighs ~400 lbs. less than my '11, probably because I went from a SCab to a SCrew.
Anyways, this is from a work trip that I did this week. Kalamazoo, MI to Chicago to Indianapolis to Muncie, IN and back to Kalamazoo. Temps in the 30's - 50's. Cruise set at 77 mph for ~500 miles of the drive. ~100 miles on country roads at 62 mph, and the rest on the job site and in town. Slight headwinds / crosswinds, or else I'd have probably gotten closer to 20.5 mpg.
I'm quite pleased with the economy on this truck thus far. ~16k miles into driving it, and 18.522 mpg life to date. Truck averages .45 mpg better on its calculation than it does when I track it by hand, so what I really got on this trip was 19.55 mpg.