Yamaha rotor oil, oil for rotary valves, 40ml The Yamaha Rotor Oil is formulated specially for rotary valved instruments. The Rotor Oil reduces friction for a smoother action and noiseless operation and also helps to prevent corrosion of the rotor. Yamaha Synthetic Rotor Oil provides excellent, long-lasting lubrication on all brass instruments with rotary valves. Great for your french horn, or any brass instrument with rotor valves.