[jcp123]

I had to dig up how they were supposed to work. These came along in the 80s, a turbofan style wheel. Audi was banned from a racing series or two for running these at all four wheels. I chose a smoky picture of Ken Block's Gymkhana 6 car to illustrate what they do: they pull air out of the wheel area for brake cooling, and when done all-around, can reduce lift forces under the car (that's what Audi was banned for). I don't know that this would be beneficial for mileage, but it sure makes a cool photo...the other two are vintage racing wheels made to do the same thing.