By Benjamin Jerew / Originally Published March 6, 2017 / National Automotive Parts Association /

From the engine to the axles and everything in between, there are tens of thousands of metal and plastic parts moving you down the road or through a field. Without lubrication, those moving parts would quickly wear out and grind to a screeching halt. Engine oil comes in plastic bottles and keeps your engine lubricated and cooled. Gear oil also comes in bottles, but has a much higher viscosity to protect heavy differential gears. The heavy grease that lubricates Spicer joints and axle bearings requires a special tool, a grease gun.

What is a Grease Gun?

We’re talking about a tool you can use to keep certain parts of your vehicle lubricated. This is basically a high-pressure pump, capable of injecting grease at up to 10,000 psi, depending on the model. For many DIYers, hand-pump models are more affordable, though some farmers and professionals might opt for an air-powered or battery-powered grease gun.

Grease comes preloaded in a paper or plastic cartridge, which is loaded into the barrel. A spring and plunger apply slight pressure to the cartridge to keep the grease flowing to the pump head. The pump head is where all the work is done, generating high pressure for grease injection. A tube or hose comes off the pump head to a coupler, which is designed to fit a grease fitting, also known as a Zerk fitting. Grease fittings are strategically placed wherever grease is needed.

Do You Need One?

Generally-speaking, if you have a grease fitting, then you’ll need this tool, but where might you find Zerk fittings? On lawn and farm equipment, you’ll find them everywhere — dozens on the average hay baler and at least a dozen on the typical tractor front end. Considering the abuse these vehicles and equipment go through, regular lubrication is an absolute must.

On automobiles, grease fittings used to be fairly common, typically on ball joints, tie rod ends and sway bar links and Spicer joints, to name a few. Over the years, though, automakers have made the switch to so-called “maintenance-free” parts, or “replace-when-broken” parts, so you might not see a single grease fitting on a late-model automobile. Many 4×4 axle U-joints are still greasable and some aftermarket replacement parts may come with “old-style” grease fittings, which some DIYers have found to last longer than OEM maintenance-free designs.

How to Use a Grease Gun

If you have to grease a fitting, doing so carefully and regularly will keep the joint lubricated and clean. First, use a rag to clean the grease fitting to prevent injecting dirt with your fresh grease. Then, fit the grease gun coupler to the fitting — it should click into place. Finally, pump grease into the fitting, but only until you see the seal bulge a little or seep from an unsealed joint. Wipe off any excess and you’re good to go!

For more information on grease guns and lubrication, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo Credit: Mass Communication Specialist Seaman Kyle Steckler, United States Navy (Wikimedia Commons).

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