Abstract: The invention relates to a method and system for increasing the output in terms of miles per gallon attainable by a conventional internal combustion engine. The improvement in m.p.g. is the result of a fuel vaporizer unit which utilizes engine collant and exhaust gases in heat exchange relationship to vaporize raw fuel. The gas vapors are collected within the vaporizer unit and then directed to the carburetor wherein it is united with air prior to entering the intake manifold. It has been found that running an engine on a mixture of gas vapors and air produces significantly improved mileage over that otherwise attainable. An additional advantage of the vaporizer unit is the resulting reduction of the amount of pollutants released into the atmosphere due to the complete and total combustion of all the vapors entering the combustion chambers.