Milwaukee M18 Cordless Grease Gun 2-Speed Tool Only 2646-20

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If you’ve ever spent half your morning hand-pumping grease into dozens of zerks on heavy equipment, you already know the problem. Your forearm burns, you’re behind schedule, and there’s still an entire fleet waiting. We put the Milwaukee M18 Cordless 2-Speed Grease Gun (model 2646-20) through weeks of testing across automotive shops and equipment yards to see if it actually delivers on its promise to eliminate this daily frustration.

This isn’t Milwaukee’s first attempt at a cordless grease gun, and that experience shows. After greasing everything from excavator pins to semi-truck fifth wheels, we found this tool fundamentally changes how fast you can complete lubrication routes. The standout? It delivers up to 10,000 PSI of pressure at 10 oz per minute, which means even the most stubborn grease points get serviced without the endless pumping.

Bottom line from our testing: this grease gun cut lubrication time by roughly 60% compared to manual pumping, and the two-speed setting proved essential for preventing blown seals on delicate fittings. But there are specific situations where this tool isn’t the right choice, which we’ll cover in detail below.

Why the Milwaukee M18 Cordless Grease Gun Stands Out

After testing numerous cordless grease guns, three features separate the Milwaukee 2646-20 from competitors we’ve used.

The two-speed transmission makes a real difference. High speed pushes grease at 10 oz per minute for main pins and heavy-duty zerks. Low speed drops to 6 oz per minute, which sounds slower but actually prevents the pressure spikes that blow out seals on older equipment. We tested this specifically on vintage tractor fittings that had failed with other guns – the low-speed setting delivered consistent pressure without rupturing the grease points.

The air bleeder valve actually works as intended. Many cordless grease guns claim easy priming, but we’ve fought with air pockets for 20 minutes on other models. Milwaukee’s valve sits at the pump base and genuinely purges air in 2-3 pumps when loading a new cartridge. This isn’t revolutionary, but it’s executed properly – something we can’t say about several competitors that cost nearly as much.

The variable speed trigger provides real control. Unlike single-speed models that dump grease at one rate, this trigger responds proportionally to pressure. Feather it for precision work on delicate bearings, or pull fully for bulk lubrication. During testing, this prevented over-greasing on ball joints and U-joints where excess grease creates its own problems.

One feature we initially overlooked but came to appreciate: the LED work light. It’s positioned perfectly to illuminate the zerk you’re targeting, which matters more than you’d expect when working under equipment or in engine bays. Small detail, but it saved us from missed fittings that would require a second pass.

Key Features & Specifications

• Maximum Pressure: 10,000 PSI – This matches commercial pneumatic guns and handles even the most resistant fittings we encountered, including seized agricultural equipment zerks
• Flow Rate: 6-10 oz/minute depending on speed setting – High speed completes a typical lube route in half the time; low speed prevents seal damage on older equipment
• Capacity: Accepts 14 oz cartridges, bulk loading, or suction from containers – We primarily used cartridges for convenience, but the bulk option saves money on high-volume operations
• Hose Length: 42-inch heavy-duty hose with grease coupler – Reaches most fittings without repositioning, though extremely large equipment may occasionally require repositioning
• Battery Compatibility: Any M18 REDLITHIUM battery (not included) – Uses the same batteries as 200+ Milwaukee M18 tools
• Weight: 7.9 lbs without battery – Manageable for extended use, noticeably lighter than comparable Dewalt model we tested
• Lock-On Button: Allows continuous operation without holding trigger – Essential for bulk greasing when hitting 30+ fittings consecutively

The standout spec is that 10,000 PSI maximum pressure. We tested this against equipment fittings that hadn’t been serviced in months (not recommended, but realistic for many operations). Where manual guns required 40+ pumps and significant effort, the Milwaukee powered through in seconds. This pressure rating isn’t marketing fluff – it’s the functional difference between completing your lube route and fighting stubborn zerks all morning.

Hands-On Performance Testing

Automotive Shop Testing: We started in a commercial truck shop servicing Class 8 semi-trucks. A typical PM service involves greasing 15-20 points including driveshaft U-joints, fifth wheel, king pins, and suspension components. With a manual gun, the experienced technician averaged 18 minutes per truck. Using the Milwaukee 2646-20 on high speed, that same route dropped to 7 minutes. The time savings compound dramatically across a full service day.

The low-speed setting proved critical on older steering components. Several trucks in the fleet had original tie rod ends with 300,000+ miles. High-speed greasing risked blowing the boots, so we switched to low speed which delivered controlled pressure. Zero boot failures across 15 trucks serviced this way.

Heavy Equipment Testing: We spent a week with an excavation company maintaining their equipment fleet – excavators, loaders, and dozers with 20-40 grease points each. This is where the Milwaukee genuinely earned its keep. A single excavator boom has 8-10 pins that require significant grease volume. On high speed with the lock-on trigger engaged, we moved through each machine in 15-20 minutes versus 45+ minutes manually.

One surprise: the tool struggled briefly on a dozer that had been neglected for months with dried grease blocking the fittings. The gun stalled momentarily but recovered after the initial blockage cleared. A pneumatic shop gun with unlimited air supply might have powered through faster, but the Milwaukee handled it after 3-4 seconds of sustained pressure.

Agricultural Testing: Farm equipment presents unique challenges – widespread grease points, outdoor conditions, and often remote locations without power. We serviced planters, combines, and tractors in actual field conditions. The cordless design shined here since there’s no air compressor available in the middle of a field. A single M18 5.0Ah battery greased an entire 16-row planter (approximately 60 fittings) with 40% battery remaining.

Temperature performance: We tested in 35°F early morning conditions with cold grease. The gun slowed slightly but continued operating effectively. We did warm the grease cartridge in the truck cab for 20 minutes before use, which helped flow rate significantly – this is true for any grease gun, not specific to the Milwaukee.

Precision Work Testing: We intentionally tested applications where over-greasing causes problems – ball joints, sealed bearings with specific grease capacities, and delicate machinery. The variable-speed trigger and low-speed setting allowed precise grease delivery. By feathering the trigger, we could deliver single-pump equivalent amounts, preventing the purging and waste that occurs when you over-fill a fitting.

What We Liked (Pros)

Massive time savings that justify the investment. Across every testing scenario, this gun cut greasing time by 50-70% compared to manual operation. For a shop servicing multiple vehicles daily or operations with extensive equipment fleets, the labor savings pay for the tool in weeks. One technician calculated he saved 2+ hours per day across his service schedule.

The two-speed function prevents costly damage. This isn’t just about speed – the low setting genuinely protects older equipment from seal blowouts and boot tears that create expensive repairs. We specifically tested this on vulnerable components and had zero failures when using appropriate speed settings. Several other single-speed cordless guns we’ve tested caused