Recently traded my 2019 2WD Laramie Crew Cab with 5.7 Hemi 3.21 and stock 20" wheels/tires... that was averaging overall 21-22 mpg thru 15,000 miles.
I now have the 2020 4WD Laramie Crew Cab with 5.7 Hemi eTorque 3.92 and 1" taller than stock tire on 20" wheels (speedometer re-calibrated) and now averaging 19-20. I was hitting close to 21, but the last couple of days I've taken it to the shop to install front spacers and then once again to install rear spacers, and they drive it like Batman in the Batmobile. They knock it down into the high 18's and by the time I get back home I'm in the mid to high 19's... but with 3,000 miles, typically keeping it in the low 20's. I did change out the AT Falken's to Michelin Defenders, since most of my driving is highway... running about 38 PSI in the Michelins.
I drive like grandpa, but we live down a 1250ft driveway, 3/4 mile down a dirt/gravel road, 11 miles down a very rough country back road, then 11 more miles of hilly road to my work... about 45 miles round trip daily. I hope I can consistently stay at around the 20 mark. If we take a bit longer trip anywhere with more highway miles, it will jump up close to 22 for a while, but after getting back home and running here and there in town, it will drop back down.
I have NOT been getting on up to speed quickly... I do gradual take offs, but I may try getting up to speed quicker to see what happens.