Empty the old grease first, then load the new cartridge

To replace grease in a grease gun, you unscrew the barrel from the handle, push out the empty cartridge or scoop out bulk grease, then insert a fresh cartridge or refill with loose grease and reassemble. The exact steps depend on whether your gun uses a sealed cartridge or an open barrel you fill by hand. Most modern guns use cartridges, which are faster and cleaner. Bulk-fill guns require more work but cost less per ounce of grease.

The whole job takes five to ten minutes. You will need a rag or paper towel, and possibly a caulk gun (if your grease gun uses standard cartridges). Some grease guns have a release button or lever on the handle that makes unloading easier; others require you to manually push the plunger backward.

Key Takeaways

  • Cartridge-style guns unscrew at the barrel and accept pre-filled tubes, while bulk-fill guns have an open barrel you load by hand.
  • Always unscrew the barrel completely before trying to remove the old grease or cartridge, or you risk damaging the plunger rod.
  • Wipe the barrel threads and plunger rod with a clean rag before reassembling to prevent grease buildup that can jam the gun.
  • The plunger should be fully retracted (pulled all the way back) before you insert a new cartridge or bulk grease.

Cartridge-style grease guns: the most common type

If your gun has a metal tube that slides into the barrel, you have a cartridge gun. These are standard on most consumer and professional models. To replace the cartridge, unscrew the barrel from the handle by turning it counterclockwise. The barrel will separate from the plunger rod and handle.

Once the barrel is off, the empty cartridge will either fall out or push out easily by hand. If it is stuck, tap the barrel gently on a workbench or use a wooden dowel to tap from the back. Do not use a hammer directly on the cartridge, as it can crack and scatter grease inside the barrel.

Wipe the inside of the barrel with a rag to remove old grease residue. Check the plunger rod (the metal shaft inside the handle) and wipe that too. Insert the new cartridge with the open end facing the barrel opening, then screw the barrel back on by turning clockwise. Tighten firmly but do not force it; you will feel resistance when the cartridge is seated correctly.

Bulk-fill grease guns: loading loose grease by hand

Bulk-fill guns have a wider, open barrel with no cartridge slot. These guns are cheaper to operate because you buy grease in bulk and scoop it in yourself. To refill, unscrew the barrel from the handle and pull the plunger rod all the way back (fully retracted).

Scoop grease directly into the barrel using a putty knife, old spoon, or the applicator that came with your grease container. Pack it down gently as you go to remove air pockets. Fill the barrel until grease reaches about half an inch from the top, then screw the barrel back on. Do not overfill, or grease will squeeze out around the threads when you explore pressure.

Wipe the barrel threads and the outside of the plunger rod before reassembling. Grease buildup on these parts will cause the gun to jam or leak over time. If you notice grease leaking from the seam where the barrel meets the handle, the plunger rod seal may be worn and need replacement.

Checking and replacing the plunger rod seal

The plunger rod has a rubber or leather seal that keeps grease from leaking out the back of the handle. If you see grease dripping from the handle or leaking around the plunger rod, the seal is worn. You can replace it without buying a whole new gun.

Unscrew the barrel and pull the plunger rod all the way out of the handle. The seal sits at the base of the rod where it enters the handle. Pry it out carefully with a flathead screwdriver or small knife. Clean the rod thoroughly with a rag, then slide the new seal onto the rod and push it back into the handle until it seats firmly. Reassemble the barrel and test with a small amount of grease.

Replacement seals are inexpensive and available from hardware stores or online retailers that sell grease gun parts. Buying a seal kit costs far less than replacing the entire gun.

Cleaning the gun after each use

Grease hardens over time, especially in cold weather or if the gun sits unused for weeks. To keep your gun working smoothly, wipe the barrel and plunger rod with a rag after each use. If grease has dried inside the barrel, soak the barrel in mineral spirits or diesel fuel for an hour, then scrub it with an old toothbrush and rinse with a rag.

Do not use water to clean a grease gun; water will rust the metal parts and mix with the grease to form a paste that clogs the barrel. Store the gun in a dry place, preferably with the plunger rod fully retracted so the seal is not under constant pressure.

Choosing between cartridge and bulk grease

Cartridge grease costs more per ounce but is convenient and produces less mess. A standard cartridge holds about 14 ounces and fits any gun with a standard cartridge slot. Bulk grease costs less and works well if you use the gun frequently, but you have to handle loose grease and keep a container on hand.

If you use your grease gun several times a week, bulk fill makes sense. If you use it once a month or less, cartridges are worth the extra cost because they do not dry out or harden in storage. Some grease guns accept both cartridges and bulk fill, depending on which barrel you attach.

Troubleshooting a gun that will not dispense grease

If you have loaded fresh grease but nothing comes out, the barrel or plunger may be clogged with old, hardened grease. Unscrew the barrel and soak it in mineral spirits for one to two hours. Use an old toothbrush or soft brass brush to scrub the inside, then rinse with a clean rag. Do the same for the plunger rod if you can remove it.

If the gun still will not work after cleaning, the plunger seal may be damaged or the rod may be bent. A bent rod cannot be straightened and usually means replacing the gun. A damaged seal can be replaced as described above. If you have tried cleaning and seal replacement and the gun still does not work, the internal check valve may be stuck, which typically requires professional repair or replacement.

Frequently Asked Questions

Can I use any grease in my grease gun?

Most grease guns work with standard lithium-based grease, which is the most common type sold in cartridges and bulk containers. Some applications require specialty grease — marine grease for boat trailers, high-temperature grease for industrial equipment, or synthetic grease for extreme cold. Check your equipment manual to see what type is recommended, but standard lithium grease works for most household and light commercial uses.

What is the difference between a caulk gun and a grease gun?

A caulk gun dispenses caulk or sealant in thin beads and has a trigger mechanism. A grease gun dispenses thick grease and uses a plunger rod or pump handle. Some cartridge-style grease guns can accept standard caulk gun cartridges, but the reverse is not true — a caulk gun cannot dispense grease. If your grease gun uses standard cartridges, you can use a caulk gun to load them, but a dedicated grease gun will work better.

How often should I replace the grease in my gun?

Replace the grease when the barrel is empty or when you notice the grease has hardened and will not dispense. If you use the gun regularly, you may go through a cartridge every few weeks. If you use it occasionally, grease may harden before the barrel empties. When that happens, unload the old grease and start fresh rather than trying to thin it out.

Can I mix different types of grease in the same gun?

Mixing grease types is not recommended because different formulations may not work well together and can reduce performance. If you need to switch grease types, empty the barrel completely and clean it with a rag before loading the new grease. This is especially important when switching between standard and specialty greases.

Why is grease leaking from the handle of my gun?

Leaking from the handle usually means the plunger rod seal is worn or damaged. This seal keeps grease from escaping around the rod as it moves in and out. Replace the seal as described above. If leaking continues after seal replacement, the rod itself may be bent or the handle may be cracked, either of which usually requires replacing the gun.