my bad. it does have 16's not 15's

 

If you don't get above 50MPH often, take your truck out of overdrive.

Also, your fuel economy going from a stop and then getting to 35MPH is about 3-5MPG. That does not matter if you are "grannying" it or if you have a relatively fast acceleration. Of course flooring it drops the MPG to about 1-2.

Get to 30MPH moderately fast then scale back on the gas pedal.

BEST ADVICE: don't drive the truck where there are a lot of stops. There is no way to get around the poor MPG.

I averaged 17.1 MPG on a 36 mile trip (35-65MPH). Every time I hit something that resembled even the slightest incline that required me to press harder on the gas pedal to maintain speed, i took the truck out of OD. In oOD, if you press down on the gas to get up the hill and try to maintain a high speed, my MPG went from 21 on the readout to about 10MPG. Accept a 10-15 MPH decrease on hills. Really steep hills require you to mash the gas to keep from going only 25 MPH. Our numerically higher gears (3rd 4th) do not like hills.

 

I get really good mileage now and after a year of semi-retirement and a 54 mile r/t drive to where I'm building my house, I have discovered accelerating very slowly and never exceeding 55 mph is the only thing that makes a difference on mine. I got around 16 mpg overall driving 90% rural highways with no stoplights. I am now regularly getting 19 mpg and have reached 20 mpg a few times by tank fillups. I have an all stock rig, except I put the double tip platinum spark plugs and platinum wires in and some mesquite tore of the bottom lip off the front bumper. I also always drive with the tailgate down. It's been my experience that it helps, despite a guy name "Jamie" saying otherwise. (: I accelerate very, very slowly and cruise at 45-50 mph. If I need to go somewhere in a hurry, I drive my 94 Plymouth Acclaim and get 30 mpg.