I just picked up my 2021 on 2 Jul, and it was showing about 17mpg on the ecometer. Yeah... well... that's all about to change. After returning back to San Angelo (280 miles from the dealership), I topped off the tank and braced for the impact of real driving.
So... 2.5 weeks of 'normal' driving around town, and I'm sitting at 13.5-ish. I have a 9-10 mile commute (one-way), which is primarily highway driving with super-light traffic, and I run out for lunch every day - so roughly 26-28 miles per day of driving. This was about normal for my 2012 Lonestar 5.7 RWD, so I figure I'm doing OK.
I have the eTorque 5.7, 4x4, Crew Cab, 3.92, 22", bed cover, and about a middle-of-the-road driving style (meaning that I'm not afraid to use the Go Pedal, but usually don't feel the need to). I have the automatic engine shut-off feature turned off (ironic, I know...), I run the A/C all the time, and I bought a 4x4 rather than a 4x2, because I really don't care what kind of fuel mileage I get. I need to get from Point A to Point B, and it's going to burn gas no matter what I'm driving. I have an old Jeep CJ-7 that gets something like 8mpg (if I'm lucky), my '71 Mach 1 gets around 16mpg (AOD & EFI), and my wife's 2015 Camaro only has ~31K miles on it, so it probably loses more fuel thru evaporation than it actually uses since she never goes anywhere.
I've owned 39mpg econo-boxes before, and actually enjoyed driving them like I stole 'em while the fuel prices were ridiculously high and out of control back in the 2000s-2010s (and it looks like we're on a track for that to happen again). But that was then and I'm in a better place now. So basically, I simply don't care what fuel mileage I get, not because I hate the environment or anything like that... quite the opposite (I have 4 cars, and only drive one at a time... that's 3 other cars that are not on the road burning fuel while I'm driving the other). But, if I were truly concerned what kind of fuel mileage I was getting, as if it really mattered, I wouldn't have bought a full-size 4x4 pick-up in the first place.