didn't see any gain from mine but they look neat so they are staying on. I figure they might give a tiny gain at most. Maybe .2-.3 mpg not really something that can be measured. Mine are also on the 12 inch wheels so they spin pretty fast when I am on the highway doing 60. I think most of the drag from a wheel comes from the tread since it is on the outer part and pumping a lot more air. Jack the car up and spin the wheels to 80mph and you can feel plenty of wind from the tread but not much around the center of the wheel.