After doing a lot of research on aircraft engine heaters, I came to the conclusion that the AeroTherm heater was my best choice and the only unit that met all of my purchase criteria: effective, lightweight, portable and inexpensive. I had decided that I wanted an electric heater and, since I fly a variety of aircraft, I needed a unit that was not permanently installed. I like the fact that the AeroTherm re-circulates heated air throughout the engine compartment, ensuring that the entire engine is heated evenly, including the oil. And with three different temperature settings and a built in thermostat, I can tailor the heater output to my specific needs on any given day.