The 16 tooth sprocket will net you about 500 RPM's lower than normal. Gains in mileage can vary from 2 mpg up to 5 or 6, it all is dependant upon your riding style, how hard you like to hit the accelorator and of course overall weight. I tried the 16 tooth, but we don't do enough highway riding for the sprocket to be an improvement. We do more back road twisties, mountains and general low gear lugging. With my weight I had to go back to the 15 tooth to gain back the torque I needed. I am even considering the 14 tooth.