snax-the 5.4 is reasonably fuel efficient.My Titan-2wd-got 20.9 mpg(miles/gallons pumped in) over a 3000 mile trip(evacuation), last Aug-Sept. The trip was almost all interstate, and my speed was~65-70. However there was lots of roadwork-45 miles per hour zones-and that really helps your mpg.The bed was fairly heavily loaded. A lot of the trip-maybe 1500 miles was at a bit of altitude(3000 ft+) and that helped the mpg. I got 25 mpg on one 300 mile leg outside Albuquerque-maybe 4000 ft+ I probably had a favorable wind(the wind blows like hell from the Tx panhandle all the way to Flagstaff,AZ..
In my normal city driving-New Orleans- I would get 12-14mpg. I finally sold it, and bought the Prius. I do miss it a little-it was a hotrod-but I don't miss $75 fillups. Luck,Charlie