|
I got it once. I was doing 80 km/h in a 90 km/h zone when an empty big rig decided he was in a hurry to get home. All I would see in my rear view mirror was his grille. Mileage jumped from 75 mpg to over 90 mpg while he was riding my bumper.
The theory is sound. You have high pressure at the front, and low pressure at the back of your vehicle. The higher the pressure differential the higher the drag. Get something back there to fill the low pressure zone and down goes the drag. That's why 2 vehicles traveling in a convoy have less drag combined than the sum of their individual drag.
|