99 f250 4x4 crewcab smokewagon. average 12-18 mpg. 12 is with 15k gooseneck, 18 is empty. 14-15 mpg towing skidsteer, mowers, or other light stuff.
subtract 2 mpg without superchips in race mode. it gets better mileage the more you crank up the programmer.
subtract 2 mpg for winter fuel.