One of the most powerful engines from os, the gf40 is a 4-stroke gasoline engine. Its quick response makes it an excellent choice for aerobatic models. If you are a scale model pilot, you will also benefit from the deeper exhaust sound of the gf40; similar to that of full-size aircraft. This os engine has the same mounting bolt pattern and mount-to-drive hub of the gt33. Its fuel economy is excellent; running on a mixture of engine oil and standard gasoline. The gf40 also features a postive crankcase ventilation (pcv) system, which recirculates blow-by gas and oil waste. This is not only environmentally-friendly, but makes the engine cleaner. Additionally, the gf40 comes with an f-6040 silencer and integral backplate. If you are a scale or aerobatic pilot, the gf40 from os engines is a great investment that will deliver excellent benefits to your model. Order yours today.