Abstract: A system for improving the efficiency of an internal combustion engine, and thereby improving fuel economy while reducing emissions is disclosed, which comprises providing a stream of vaporized fuel from a vaporization chamber to the air intake stream of the engine. Surprisingly, this system is suitable for use with both diesel and gasoline engines of conventional and rotary type, as well as jet engines and other internal combustion engines. Entraining about 0.05-1.0% of the total fuel consumed in the air intake stream according to this system results in a substantial improvements of fuel economy (up to 36% improvement over the same engine without the vaporization system) while reducing pollutants at least one order of magnitude below the current standards.