Abstract: A device for injection of molecular hydrogen and oxygen into the combustion chambers of a gasoline engine, along with the fuel-air mixture, to improve fuel efficiency and to reduce and in some cases eliminate engine emissions. The hydrogen-oxygen/hydrocarbon fuel system includes: a water source; an electrolytic chamber, an anode and a cathode mounted into the chamber in closely spaced fashion from one another; two fluid lines to fluidingly connect the water source and the fuel tank to the chamber; and an electrical power source, for electrically charging the anode and cathode.