I have a 2017, 4x4 with the 3.73 rear end. Right now I'm seeing 13.5 on the screen with half tank running about 100 miles highway, 50 miles around town. ATM I have 600 miles on the truck. When running the highway I usually am running 70-80 mph. Can't complain considering my 04 f150 2wd with the 5.4 and 3.55 axle got about 14-14.5 with the same style driving. I expect that number to increase a little after some more miles get on the truck. From what I was reading the 4.30 rear axle isn't much worse on mileage, maybe a little better around town since the lower gears help with low speed accel. I had planned to order the 4.30 but found a great deal on the dealer lot.