I got 20.3 last summer with the cruise set on 68mph bone stock truck had 3000 miles on it.Its a 5.4 crew 4x4 150wb with 3.73s.Thats checking it the old way fill up all the way set trip fill up all the way again.I average 17 city highway mix.I have not checked sence tuner,intake,exhuast upgrade but do notice a improvment around town anyway.13mpg is terreble but you live in utah you have huge hills,high altitude.

 

4.2L V6, Troyer Performance electric fans, ASP underdrive pulley, Airaid cold air intake, Heartthrob Deep-Tone Dual Kit exhaust, B&M Racing Hi-Tek Cooling System, Mag-Hytec 4R70 DD transmission pan & 8.8 differential cover, 4.10:1 Ford Racing Performance Parts ring & pinion, synthetic fluids; on 35" AT tires.

 

Wow, 3 that are getting more than 13 MPG! Must be some kind of record!

 

hmmm thats good....i have the 36 gallon with a Banks Intake and PHP Tunes and i've been averaging about 120 to 150 miles to a quarter tank which is pretty damn good!!! and I have yet to do my dual magnaflow setup.

Usually I fill up at 1/4 and I have about 240 miles but now i've had from 300 to 380 or more sometimes.....I love it.

 

My 5.4 4x4 with 3.73s is bone stock except for the tires and I get around 12ish in the winter with running it longer and using 4x4. I got consistant 16s and somtimes 17 in the city last summer, and not by driving like a grandpa either. Just normal excelerating off the line and not by flooring it every time like some others.