Aircraft engines need preheating to be able to start without damage in cold weather. It is possible to do this efficiently by placing a small amount of heat in the proper places. An installed electric system is very convenient and easy to use. A good design will be light weight and energy efficient. Corrosion in engines that operate in cold weather can be reduced or eliminated by the right preheater design and the proper operation of the engine. Some designs of preheater systems aggravate other problems. A certain amount of caution is needed in selecting the system. The unit should be specifically matched to the aircraft and engine.