The present invention provides an engine oil additive for enhancing engine function and improving fuel economy, the additive allowing engine oil particles to be ionized and fragmented by natural minerals simply and inexpensively without a separate device, such that the interval at which the engine oil particles come into contact with the inner wall of an engine decreases and the plasma state is maintained so as to prevent cations and anions from coupling to each other in liquid, and fuel economy is improved while engine activity is enhanced. To this end, the additive is obtained by mixing 1.5-2 wt % of tourmaline, 0.8-1 wt % of sericite, 0.5-0.8 wt % of monazite and 0.3-0.5 of elvan, in a powder form of 2-3 μm into 95.7-96.9 wt % of a base oil so as to be added to an engine oil to be injected into an engine.