On the semi's they tell us for the air foils to work, the trailer needs the be snug (within 3') of the tractor. Most pickup to 5'r combinations you will be spread out to far. The newer 5'rs have aerodynamic noses to help the air flow around them. Heartland claims a 1-2 mpg improvement with their design. Each rig is different and thus they each require their own solution.
If it makes you feel any better I ran the numbers for the trucks assigned to my location for last week. 21 tractors ran a little over 44,000 miles, consumed around 7,700 gallons of diesel at a fleet average of 6.12 mpg. Our target is 6.2 mpg as we are a short haul operation. To me, 10-12 mpg looks great! Yes, I know its apples to oranges. Speed, idle and tire pressure are killers to mpg. I'd start there. What about when your not hooked up? What happens to your mpg when your just running around town with it up there and no trailer?
