Abstract: An automatic oil additive injector is disposed over the drain opening in a bottom wall of an engine oil pan and extends into the oil pan. A side port is provided in a housing of the injector for allowing oil to drain therethrough when the oil drain plug is removed. Primary and secondary valve assemblies and a pump operator provided in the housing are activated upon removal of the drain plug to allow a chamber therebetween to fill with a predefined volume of additive, preferably silicone fluid, from a reservoir of the injector and which, upon engagement of the drain plug, dispense the fluid into the oil pan at each oil change to decrease aeration of the oil. In a second embodiment, the additive injector and reservoir are incorporated in the lubricating oil filter header.