The mention of 50-mpg fuel economy normally implies econobox driving or an expensive hybrid. But you do not have to give up good looks or buy a high-priced vehicle in order to cut down on gasoline. Tri-Magnum is an excellent example of how ultralight construction can result in both high fuel economy and sports car performance. This motorcycle-based three-wheeler performs like a production sports car, and it still delivers fuel economy roughly equivalent to that of the original motorcycle. The key constant on performance is the power-to-weight ratio.