Tested a lawn edge Air dam 2 weeks ago and saw no appreciable gain and possible loss of mpg's at cruise. pics below of lawn edging.
the air dam has been cut to act as a deflector for both the front tires.
Also if you look close on the first pic you will see i taped the holes in my steelies, there was no gain noticed, however my wheels/caps stay clean much longer than they used to
