It's all about driving style. I have almost the worst Ranger from the factory for mileage...4.0 liter automatic 4x4 with 4.10 gears. I get about 18 city and about 21 highway because I'm light on the gas pedal and never put my toe into that gas pedal unless I need to get up to speed. Highway, I go no higher than 65.
Just take it easy. Save the power for the woods.