I have almost 5000 miles on 2019 Longhorn, Hemi (no eTorque), 3.21 gears and I average around 16 MPG city and 19 to 20 MPG on the highway. My truck is loaded (extra weight) and has the 22" wheel option.
If I remember correctly my 4TH Gen Hemi did a little better in the MPG department. Still, in the end it is a 5000 pound truck so I am not complaining; it sure is a lot better then the Tundra I had. The only truck that got better MPGs was my 2016 F-150 Platinum with the 3.5 EB (felt moe powerful as well).
19 Ram 1500 Laramie LongHorn Hemi, 87 Monte Carlo SS, 14 Mercedes GLK 350 (wife's)
One of the "Quiet Professionals"