Before I added the 33” I got 18-20 from the 3.0 sometime a little more if a lot of HY.
IMO… there is one main reason, “the Lead Foot Syndrome”.
85% of gas consumption is taken up in 15% of your driving style; acceleration, up-hill acceleration, and passing and of course trying to get the 3.0 to do 90 mph, but that is extra.
Chg’g your driving style, easy take offs, shift at 1500 to 2K and ease into it, don’t over accelerate up hills, and easy passing, in other words keep your foot OUT OF IT !
luck to ya.
4x4, 5sp, Std Cab, Stepside, E4 Red
4” Lift - Coil-Overs, 6” SkyJacker Leafs - No Blocks (Mistake)
31 Spline FX4 Rear Axle, 4.56s and OX Locker, Hurst Shifter w/Optional Stick and "Made by Grev" alignment adapter