The invention produces and meters a constant supply of volatile gasoline vapors into the cylinders of an internal combustion gasoline engine. The vapors are produced by releasing them from liquid gasoline through pressure differential inside a closed vaporizer container (16). Vapor is transferred from the container to the fuel delivery mechanism (14) by introducing the vapor into one or more constant vacuum inlet ports of the fuel delivery mechanism (14). A variable gascock valve (70) regulates the flow of vapor. These constant vacuum inlet ports, and lines thereto, are standard components of all modern automobile engines and require no modification for installation. All gasoline burned by the engine first passes through the system's vaporizer container (16) where a portion of the available vapor (free vapor) is released and transferred to the fuel delivery mechanism (14). Unvaporized liquid gasoline within the container (16) is concurrently pumped to the fuel delivery mechanism by an auxiliary fuel pump (44).
