 Have 17,500 and love the truck. Interior is beautiful and convenient. Can ride for days and feel fresh. Pulling a 40 ft horse trailer with 8- 10 horses. Have no problem with power.  Gas mileage is where I expected it. 10 to 15 mpg hauling 14 to 17 off hook.  Notice a big difference in mpg from 55 to 65. No problems so far. Prior truck was gmc 3500. No comparison.