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I think the point is that if a wind (air velocity over a surface) exists it can be used to propel a vehicle in any direction, most efficient being with the wind.
So wind can be used, converted mechanically is probably most efficient, to push against the surface (ground or water etc.) and propel the vehicle forwards, but if there is no wind relative to that surface then just like sailboats in dead calm air, she aint goin nowhere. No matter how fast you drive airspeed is stationary with respect to the ground and hence you cannot use this percieved wind as a form of perpetual motion.
You could however make a small wind powered model that drives around on your bonnet to amuse you while you drive, but it will probably increase your overall drag too.
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