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Keeping heavy equipment and farm machinery properly lubricated is essential for reducing wear, preventing breakdowns, and extending service life. But manually pumping grease into dozens of fittings can be exhausting and time-consuming. That's why cordless grease guns have become a must-have tool for mechanics, farmers, and equipment operators who need to get the job done quickly without tethering themselves to a compressor or hand pump.

Milwaukee offers two popular cordless grease gun platforms: the heavy-duty M18 line and the compact M12 line. Both deliver outstanding performance, but they serve slightly different roles depending on the scale of your work. In this article, we'll compare the M18 vs M12 cordless grease gun options, highlight key differences in power, runtime, and portability, and help you decide which model is best for your heavy equipment and farm maintenance tasks.

Milwaukee M18 Cordless Grease Gun: Raw Power for High-Volume Jobs

The Milwaukee M18 cordless grease gun is built for demanding environments where you need high pressure and high flow rates. Whether you're greasing excavator pins, tractor linkages, or conveyor bearings, the M18 platform delivers up to 10,000 psi of pressure and a flow rate that can handle even the most stubborn, packed fittings. It's compatible with the full M18 battery lineup, including the high-capacity M18 High Output 6.0Ah battery pack (4-pack) that lets you work all day without swapping batteries.

One of the standout features of the M18 grease gun is its variable speed trigger, which gives you precise control over grease flow. You can start slowly to avoid blowing out seals, then ramp up the speed for faster application. The tool also features a built-in LED light to illuminate dark undercarriages or engine compartments, and a durable metal gear case that withstands drops and rough handling on the jobsite.

• Best for: Heavy equipment, farm machinery, industrial lubrication, high-volume fleet maintenance

Milwaukee M12 Cordless Grease Gun: Compact and Convenient for Tight Spaces

If you often work in tight spaces or need a grease gun that's easy to carry around the farm, the Milwaukee M12 cordless grease gun is an excellent choice. Powered by the M12 REDLITHIUM battery system, this compact tool delivers up to 5,000 psi of pressure—plenty for most light to medium-duty applications like greasing lawn mower spindles, small tractor fittings, or ATV suspension components. Its lightweight design (under 5 pounds with battery) reduces fatigue during extended use.

The M12 grease gun also features a flexible hose that makes it easier to reach awkward fittings, and it includes a built-in bleeder valve to remove air from the system quickly. While it doesn't match the M18's raw pressure, it's more than capable for routine maintenance on smaller equipment. Plus, it shares batteries with other M12 tools like the M12 FUEL 12V Lithium-Ion Brushless 5-3/8 in. Cordless Circular Saw or the M12 FUEL HATCHET Pruning Saw, making it a versatile addition to your existing M12 collection.

• Best for: Light to medium-duty lubrication, tight spaces, farm and ranch maintenance, DIY equipment care

Key Differences: M18 vs M12 Cordless Grease Gun

When choosing between the M18 and M12 grease guns, the main factors are power, runtime, and portability. The M18 model delivers higher pressure (10,000 psi vs 5,000 psi) and a faster flow rate, making it ideal for heavy equipment with large, dirty fittings that require more force to push grease through. It also runs on larger M18 batteries, which provide longer runtime—especially when paired with a high-capacity pack like the M18 High Output 6.0Ah battery pack (4-pack).

The M12 model, on the other hand, is more compact and easier to maneuver in tight spaces. It's also lighter, which reduces arm fatigue during long greasing sessions. However, its lower pressure means it may struggle with heavily caked or rusted fittings that need a strong initial burst. For most farm maintenance tasks like greasing hay balers, grain augers, or small loaders, the M12 is more than adequate. For heavy construction equipment or large earthmovers, the M18 is the better choice.

• Tip: If you already own M12 tools, the M12 grease gun shares the same battery platform, saving you money on additional batteries and chargers.

Battery and Runtime Considerations

Battery compatibility is a major factor when choosing between the M18 and M12 grease guns. The M18 model works with all M18 batteries, including the compact 2.0Ah pack for lighter weight or the high-capacity 6.0Ah pack for all-day use. If you're working on a large farm or fleet, investing in multiple M18 High Output batteries ensures you never run out of power mid-job. The M18 grease gun also features a fuel gauge on the battery so you can monitor remaining charge at a glance.

The M12 grease gun uses M12 batteries, which are smaller and lighter. A standard 4.0Ah M12 battery provides enough runtime for several hours of intermittent greasing. For longer sessions, you can keep a spare M12 4.0Ah battery pack charged and ready to swap. The M12 platform is also ideal if you already own other M12 tools, as you can share batteries across your entire M12 lineup.

• Tip: Always keep at least two batteries charged when using a cordless grease gun to avoid downtime.

Which Milwaukee Grease Gun Should You Buy?

For heavy equipment operators, construction crews, and large-scale farm maintenance, the M18 cordless grease gun is the clear winner. Its high pressure and flow rate can handle the toughest fittings, and the long runtime from M18 High Output batteries means fewer interruptions. If you frequently grease multiple machines in a single day, the M18 will save you time and effort.

For smaller farms, hobby farms, or mechanics who work on compact equipment, the M12 cordless grease gun offers a great balance of portability and performance. It's easier to carry around, fits into tight engine compartments, and still delivers enough pressure for most routine greasing tasks. Plus, its compatibility with the M12 battery system makes it a smart addition if you already own M12 tools like the M12 FUEL circular saw or M12 HATCHET pruning saw.

• Consider your typical workload: heavy equipment demands M18; light to medium maintenance is well-served by M12.

Whether you choose the M18 or M12 cordless grease gun, Milwaukee offers reliable, high-performance tools that make lubrication faster and easier. For heavy equipment and farm maintenance, the M18 model delivers the power you need to tackle the toughest jobs. Explore the M18 grease gun options and battery packs available at milwaukeetool.com to find the perfect setup for your shop or farm.