Grease Gun: What It Is and How to Use It

A grease gun is a lubrication tool that delivers grease under pressure to specific points on machinery and hardware. It connects to small ports called zerk fittings (also known as grease nipples) and pushes grease into bearings, bushings, and pivot points. By applying grease where it’s needed—and only where it’s needed—you reduce friction, prevent wear, and keep moving parts running smoothly.

How a Grease Gun Works

A typical grease gun has a few basic parts:

Barrel: Holds the grease, usually in a replaceable cartridge.
Plunger and spring: Push the grease toward the head of the gun.
Head and pump mechanism: Operated by a lever, trigger, compressed air, or a battery-driven motor.
Hose or rigid tube: Guides the grease to the fitting; flexible hoses help reach tight spots.
Coupler: Snaps onto the zerk fitting to create a seal and prevent leaks.

When you pump the handle or pull the trigger, the gun pressurizes the grease and forces it through the coupler into the fitting. Inside the part you’re greasing, passages direct the grease to bearings or sliding surfaces.

Common Uses in DIY and Home Maintenance

You’ll find grease fittings on many items around a home or small property. Typical jobs include:

Lawn and garden equipment: Mower deck spindles, wheel bearings on garden carts, lawn tractor steering pivots and front axle bushings, snowblower auger shafts and impeller bearings.
Automotive and trailers: Greasable suspension components (ball joints, tie-rod ends, U-joints), trailer suspension shackles, hitches and couplers. Some wheel hubs use add-on systems like Bearing Buddy; follow the manufacturer’s procedure.
Outdoor hardware: Gate hinges with zerks, winches, and pulleys.
Shop tools and machinery: Drill press quills (if equipped), bearings in small machinery, and pivot points on presses and jacks.

Not everything needs grease from a gun. Many door hinges, garage door rollers, and locks prefer oil or a spray lubricant. Check the manual or a lube chart for your equipment.

Types and Variations

Grease guns vary by how they’re powered and how they’re loaded.

Manual lever: High pressure with each stroke. Good for stubborn fittings but requires two hands. Reliable and affordable.
Manual pistol-grip: One-handed operation; handy in tight spaces. Slightly lower pressure than lever styles but very convenient for homeowners.
Pneumatic (air-powered): Runs from a compressor. Great for frequent use in a shop; not as portable.
Cordless (battery-powered): High output and consistent pressure with minimal effort. More expensive and heavier, suited to frequent or heavy-duty use.

Loading methods:

Cartridge-loaded: Most common. Uses standard 14 oz cartridges (3 oz mini cartridges are available for compact guns). Clean and quick.
Bulk-fill: Scoop grease directly into the barrel from a pail. Cost-effective for high-volume users.
Suction-fill: Draws grease from a container by pulling the plunger.

Accessories and variations:

Hoses and extensions: Flexible hoses (12–18 in.) reach tucked-away fittings; rigid tubes offer better control on open fittings.
Couplers: Standard jaw couplers fit most zerks. Locking couplers reduce leaks and mess. Needle and right-angle couplers reach recessed or flush fittings.
Bleed valves and clear barrels: Bleed valves make priming easier; clear barrels help confirm grease type and level.

How to Choose a Grease Gun

Match your usage: For occasional yard equipment, a pistol-grip manual gun with a flexible hose is easy to handle. For frequent maintenance or farming, consider a lever or cordless model.
Check pressure and output: Most manual guns reach 5,000–10,000 psi. A higher output per stroke speeds large jobs; lower output gives finer control on small fittings.
Comfort and control: Look for a non-slip grip, a swivel hose, and a locking coupler.
Ease of priming: A bleed screw or valve saves time after loading a new cartridge.
Cartridge size: Standard 14 oz is widely available; a compact 3 oz gun packs well in a tractor or truck.
Grease compatibility: Plan to use common NLGI #2 multi-purpose or lithium complex grease unless your manual specifies otherwise. If you need specialty grease (marine, food-grade, high-temp, or moly/EP), label the gun so greases don’t get mixed.

Step-by-Step: Loading and Using a Grease Gun

Choose the right grease: Most outdoor equipment uses NLGI #2, lithium complex multipurpose grease. For wet environments (boat trailers), marine grease is common. For high load pins and bushings, a molybdenum-disulfide (moly) or EP grease may be recommended. Always check the manual and avoid mixing incompatible grease types.
Load the cartridge: Unscrew the head from the barrel. Pull the plunger rod fully back and lock it. Insert the cartridge with the open end toward the head, remove the seal tab, and thread the head back on. Release the plunger.
Prime the gun: Crack the bleed valve or loosen the head a half-turn and pump until grease flows steadily; tighten the head/valve.
Prep the fitting: Wipe the zerk clean to keep grit out of the bearing. Replace damaged or clogged zerks before greasing.
Attach the coupler: Snap it squarely onto the zerk. A locking coupler helps prevent blow-off.
Pump slowly: Apply 1–3 strokes for small bearings, more for larger ones. Watch for fresh grease purging from relief points or seals; stop as soon as you see it. Over-greasing can push seals out.
Remove and clean: Release the coupler, wipe any excess grease, and cap the coupler to keep it clean.
Record maintenance: Note the date and number of pumps to build a lube schedule.

Maintenance and Care

Keep it clean: Dirt ruins bearings. Always wipe zerks and the coupler before and after use.
Label the gun: Mark the grease type and color on the barrel. Use separate guns if you use different greases.
Store correctly: Keep the gun in a cool place, horizontal, with pressure released to reduce oil bleed and separation. Use a dust cap on the coupler.
Inspect parts: Replace worn coupler jaws, cracked hoses, and leaky seals. Keep spare zerks in your toolbox.
Mind the weather: In cold climates, keep the gun warm so NLGI #2 grease flows. For extreme cold, a lower NLGI grade (e.g., #1) may be specified.

Common Mistakes to Avoid

Over-greasing: Blowing out seals or forcing grease into areas it shouldn’t go.
Mixing grease types: Not all thickeners are compatible (e.g., lithium vs. clay or calcium sulfonate). Mixing can cause softening or separation.
Skipping cleaning: Pushing dirt through the fitting shortens bearing life.
Ignoring air pockets: A poorly primed gun sputters and under-lubricates.
Wrong lubricant: Using grease where oil is specified, or using general-purpose grease where high-temp or marine grease is required.
Wrong coupler or angle: Leaky connections waste grease and make a mess.

Related Terms

Zerk fitting/grease nipple: The small check-valve fitting that accepts the coupler.
Grease cartridge: Pre-filled tube of grease for cartridge guns.
NLGI grade: A measure of grease consistency; #2 is common for general use.
EP/moly grease: Grease with extreme-pressure or molybdenum additives for heavy loads.
Bearing/bushing: Rotating or sliding components that reduce friction and require lubrication.

Practical Examples

Lawn tractor deck spindles: Every 25 hours, wipe each zerk, clip on the coupler, and give 1–2 pumps until fresh grease purges from the seal. This prevents heat buildup and spindle failure.
Trailer suspension shackles: With weight on the suspension, grease each fitting until you see fresh grease at the bushing. Wipe off excess to avoid attracting grit.
Snowblower auger bearings: Before the season, apply a couple of pumps per zerk. After heavy use or washing, re-grease to push out moisture.
Gate hinge with zerk: Attach a needle or standard coupler, pump until movement feels smoother, and wipe away extra grease to keep dust from sticking.

With a little practice and the right grease, a grease gun helps you perform precise, clean lubrication that extends the life of your tools, vehicles, and outdoor equipment.