My 2011 CC Dually with 3:73 gears gets a best of 17 and a half mpg on the highway at 70 mph and 14-15 in town. My old 97 7.3 got 20.7 mpg with 4:11 gears at 55 mpg, about 17 at 65 mph. I'm not complaining, but I too wonder how some of these trucks are supposedly getting 18-20 mpg driving 80 mph while I'm using the cruise control and staying under 2000 rpm. The power this thing makes offsets the mediocre mileage but I don't understand why we're not all averaging about the same mileage.
2011 F350 4x4 XL Crew Cab Dually
2010 Keystone Fuzion 405 Toyhauler