Can't understand all these poor mileage complaints. My 2013 1500 crew cab with 5.7 hemi, 6 speed auto and 3.92 rear end running on 87 octane, with OEM tires or I recently replaced them with Toyo Open Country AT II's and I typically get 18 to 19 mpg on the highway, 13 to 15 in town. I figure mileage manually and it's very close to what the computer says. I do drive with a light foot, but highway speed is usually 60 to 70 mph. My truck has 44,000 miles on it and I just did it's first spark plug change. Haven't noticed any difference in performance or fuel mileage. My son's 2017 1500 extended cab, 5.7 L , 8 speed auto with 3.21 rear end will usually get about 2 to 3 mpg better then my truck. At 70 mph he's turning 500 rpm less then I am.