How to Use a Grease Gun | Step-by-Step Lubrication

A grease gun delivers grease through Zerk fittings on vehicles and machinery, and using one correctly requires loading a 14-ounce cartridge, priming the system to remove air, and pumping with steady strokes until fresh grease seeps from the joint.

Lubricating bearings, ball joints, and U-joints keeps equipment running longer, but a grease gun is only as good as the technique behind it. The most common failure isn’t the tool — it’s air trapped inside that stops grease from flowing, or a contaminated cartridge that introduces metal slivers into a clean system. The process breaks into three phases: loading, priming, and application.

Loading a Grease Gun With a Cartridge

Most manual grease guns use standard 14-ounce cartridges. Start by pulling the plunger (follower rod) handle back fully and locking it in the retracted position. Unscrew the barrel from the head assembly counter-clockwise and remove any old cartridge — use pliers if it’s stuck, but watch for sharp edges.

Prepare the new cartridge by removing the plastic cap, but leave the metal foil seal in place until the barrel is reassembled. Slide the cartridge into the barrel with the metal cap facing out (the open end toward the pump head), ensuring the follower plate sits between the cartridge and plunger. Screw the barrel back onto the head assembly securely, then remove the foil seal.

If you plan to buy a quality gun rather than borrow one, our tested roundup of the best grease guns covers lever-handle and pistol-grip models suited for home and shop use.

Priming the Gun to Expel Air

Air trapped between the pump head and grease cartridge is the single most common cause of frustration. Push the plunger handle forward to force grease toward the head. If your gun has an air-bleeder valve, open it to let trapped air escape. Pump the handle or trigger until grease flows steadily from the coupler tip with no bubbles — that’s your success cue.

Once the flow is steady, close the bleeder valve. If no grease appears after several pumps, remove the plug on the gun head’s end and continue priming until air is forced out. A high-pressure lever-type gun can reach up to 10,000 PSI, so controlled priming prevents pressure spikes later.

Greasing the Zerk Fitting Correctly

Zerk fittings (also called grease fittings) are the small metal nipples found on ball joints, tie-rod ends, U-joints, and most machinery pivot points. Clean the fitting with a rag before attaching the coupler — dirt forced inside is the fastest way to wear out a bearing.

Push the coupler onto the fitting until it clicks or latches securely. For lever-type couplers, flip the lever to lock. Pump with smooth, consistent strokes — jerky or rapid motion makes it harder to see when the joint is full. Some high-pressure models deliver roughly 28 strokes per ounce, so a few firm pumps are usually enough.

When to Stop and Clean Up

Stop pumping the moment you feel resistance or see a small amount of fresh grease escaping from around the joint. This seepage means the cavity is full; pumping longer risks damaging seals or blowing out the bearing. Release the coupler slowly — some guns have a pressure-release mechanism — then wipe away excess grease with a clean rag.

Avoid mixing grease types. Lithium-based and calcium-based greases can chemically react and cause bearing failure. Mark each gun by the grease it contains, or clean the barrel thoroughly before switching formulations. High-pressure guns demand controlled coupler release: pulling the coupler off at an angle can strip threads, so pull straight or wiggle gently if it’s stuck.