Before V3 I was in the 22~22.5 range in the summer and had previously (2018) peaked into the low 23's during a bet with a co-worker. My truck had a makeover in 2017~2018 where I took it back to stock height, lightened up rotating mass on the engine, driveline and wheels with custom tuning (by me using HP tuners) to leverage all the changes. That got me into the 20~22 range consistently and had been averaging 21.0x mpg year round thru 2021. Summer time would bring 22's.
Here is how it looks these days... stock.
I experimented with a lot of aero changes and found 3 things that really stood out, bed seals from the top of the bed down to the body line above the tires, the 2nd air dam and the front wheel liner vents. Never did go back and work on the bottom side of the truck, probably a lot to be gained there.