Abstract: Precombustion ionization devices are disclosed for treating the vaporizable liquid fuel in internal combustion engines, including at least one foraminous member prepared from a catalytic metal having an oxide coating on the surface thereof. The foraminous member, or screen, is spaced from the carburetor and the engine intake of the internal combustion engine by means of a supporting gasket. The disclosed precombustion ionization devices may also be attached to a source of relatively high voltage, resulting in increased ionization of the vaporizable liquid fuel thereby, and preventing electropolishing of the metal oxide coating.