Being retired with lots of time on my hands, I've been checking my mileage for the last 17K plus miles. About the last 3 years. I have an ext cab, 3.0, with auto and stock 3.73 gears. I tack about 2600-2700 RPM at 70 MPH. My best tank during that time was 21.7. That was almost all highway at about 70-75 MPH. Mostly on cruise control. Worst was 13.6, all city driving. Probably a bunch of full throttle, jack rabbit starts on that one. Usually I get about 19-20 on the highway and about 15 around town. Overall average for 17K miles is 16.9.
Two things: 1:About 75-80% of my driving is around town. So I think my overall MPG would be 1 or 2 MPG higher if it where a 50/50 mix.
2:My truck is probably 700-800 lbs heavier than stock because of the hard tonneau cover and all the sound proofing and audio equipment I have.