A lubricator adds controlled quantities of tool oil into a compressed air system to reduce the friction of moving components. An aerosolized stream of oil is injected into an air line by a pneumatic lubricator to lubricate the internal moving components of pneumatic tools as well as other devices such actuating cylinders, valves, and motors. An FRL (Filter-Regulator-Lubricator) unit should always have the lubricator as the last component.