Abstract: An air foil system that can include a complimentary pair of inner and outer air foil elements forming an openings and exits in one cross section, the opening being from 2 and 6 inches in height in the one cross section and the exit being from between about ¾ and 4 inches in height in the one cross section. The complimentary inner and outer air foil elements may form a compression chamber between the complimentary entrance and exit edges, the compression chamber having a height in one cross section that is from ½ inch to about 3 inches. A mounting assembly may be operatively connected to the inner and outer air foil elements for aligning the opening within 5 inches of the rearmost portion of rear-facing portion and mounting the air foil elements to the rear-facing portion of the vehicle.

Abstract: The specification describes a preferred embodiment of the square-backed vehicle air foil 10 for attaching to a vehicle 12 adjacent an upper rear edge 21 for projecting into a horizontal airstream "S" for subdividing the airstream into an inner or first airstream layer S.sub.1 and an outer or second airstream layer S.sub.2. The assembly 10 has an inner air foil element 32 that directs the first airstream layer rearward and then rearward and downward over the rear edge 21 and then downward at a first velocity along the rear vehicle panel 21 to form a first air curtain along the rear panel to keep the rear panel clean. The assembly 10 has an outer air foil element 34 that, in cooperation with the inner foil element 32, directs the second airstream layer S.sub.2 rearward along the roof panel while accelerating the layer S.sub.2. The layer S.sub.