I have an 08 WRX hatch and picked up the OEM roof bars off eBay for cheap and got the Fairing and a bunch of other Yakima racking stuff through a friend/dealer. I had to modify the fairing mounts to attach to the OEM bar but it was super easy. I always have on my car: crossbars, fairing, and two of the Yakima Raptor Aero bike racks and monitor my fuel mileage on every trip and haven't noticed any decrease at all. With both my bikes on, yes, but not just with the mounts. I also drive my car like an old man and at the speed limit, which makes a huge difference for fuel economy.