A grease gun which uses a piston to mechanically push grease from a standard tube without the need for air pressure. A grease tube chamber is sized to hold a standard tube of grease, and may be closed at a first or front end by a cap with a dispensing nozzle. At a second end, a piston assembly includes a plunger rod with a piston that may be advanced towards the front end by a drive handle assembly. As the piston advances, it enters into the open rear end of a grease tube, pushing the grease forward where it is dispensed through the nozzle on the cap. When not in use, the plunger rod is urged rearwards by a spring, pulling the piston away from the grease to reduce potential leakage.
