Abstract: The lubricator, according to the embodiment shown, comprises a lubricant storage chamber, which is connected between a lubricant supply line and lubricant discharge line, in which to receive a stored "charge" of lubricant. The chamber is evacuated by a plunger carried by a piston, the latter being operated by pneumatic pressure when the device to be lubricated is started up or turned "on". By way of example, the lubricator will supply a charge of lubricant to an air motor on motor start up; the plunger-operating piston is translated by a portion of the compressed air which is conducted to the air motor. A further piston-carried closure element is interposed in the lubricant discharge line to insure that, where the lubricant supply is under pressure, lubricant will not be conducted into the lubricant discharge line until the machine to be lubricated is started.