Milwaukee M12 Fuel Surge 2551-20 Impact Driver Review

Milwaukee 2551-20 Angle 5

Quick take

The Milwaukee M12 Fuel Surge 2551-20 is a hydraulic impact driver in Milwaukee’s flagship Fuel lineup. Hydraulic impact drivers operate differently than hammer-based models, delivering a less violent and muted impacting noise. Unsurprisingly, the 2551-20 shined in our noise performance tests, offering as close to “whisper” quiet performance as you’ll find for an impact driver. Beyond noise, you’ll get a tool with outstanding build quality, a compact footprint, a durable brushless motor, drive mode versatility, and a best-in-class tool and battery warranty. However, the 2551-20’s battery run time performance lags the competition, and you’re not going to win any speed contests driving big structural screws and lag bolts. Accordingly, it’s best for prosumers that appreciate a high-end tool that is precise and breezes through light and medium-duty driving jobs. It’s also a solid pick for woodworking and carpentry.

Brand Milwaukee
Platform M12 Fuel Surge
Motor Brushless
Tested torque in-lbs 472.8
IPM 3,400.0
Drive modes 4
Collet 1/4-inch hex
Same as M12 hydraulic

Global rankings

21 models tested

TestResultRank
Driving speed (sec.)24.817
Torque (in-lbs)472.820
Battery run time (min.)26.018
RPM2,972.012
Bare weight (lbs)2.029
Impacting noise (dBA)86.11

Editorial opinion

Methodology used: Light duty

Editorial rating

4.36 / 5 stars

Pros

  • Outstanding noise performance
  • Compact footprint
  • Versatile drive modes
  • Durable brushless motor
  • Fantastic tool and battery warranty

Cons

  • Poor battery run time
  • Slow driving speed

Recommended configuration

2551-22

Includes (1) M12 Red Lithium CP 2Ah battery

Series lineup

Model #PlatformDrive ModesTorqueIPMReview
2462-20M121491.4 in-lbs3,300.0Full review
2551-20M12 Fuel Surge4472.8 in-lbs3,400.0Full review
3453-20 (Gen 3)M12 Fuel4696.0 in-lbs4,000.0Full review

Lab results

Torque

Milwaukee 2551-20 Torquemeter
Milwaukee 2551-20 Torque Charts

Max torque drive mode 1 (in-lbs): 472.8
Max torque drive mode 2 (in-lbs): 241.8
Max torque drive mode 3 (in-lbs): 73.8
Max torque drive mode 4 (in-lbs): N/A

All hydraulic impact drivers offer lower torque output than equivalent models with anvil-based impacting mechanisms, including the 2551-20. This impact driver generates enough torque to bust loose some lug nuts and light bolts, but it isn’t powerful enough to tackle more stubborn fasteners. The torque profile is one of the trade-offs made for the quieter and smoother impacting experience.

Compare torque test results

RPM

Milwaukee 2551-20 RPM Charts

Max RPM drive mode 1 (fwd.): 2,972.0
Max RPM drive mode 2 (fwd.): 1,952.0
Max RPM drive mode 3 (fwd.): 885.0
Max RPM drive mode 4 (fwd.): 2,982.0
Max RPM drive mode 1 (rev.): 3,011.0
Max RPM drive mode 2 (rev.): 2,036.0
Max RPM drive mode 3 (rev.): 927.0
Max RPM drive mode 4 (rev.): 2,773.0

The 2551-20 is moderately fast for a 12V impact driver, helping to set screws quickly. One potential risk of a high RPM is cam-out and stripping screws. This risk is more of an issue for more powerful 18V impact drivers. The 2551-20 is well-balanced and impresses with its ability to avoid cam-out and stripped screws.

There is no significant measured RPM difference between forward and reverse for each drive mode. Some models increase RPM in reverse for specific drive modes to help bust loose bolts and stubborn screws. We didn’t encounter a situation where the 2551-20 was underpowered removing screws.

Compare RPM test results

Driving speed

GRK total driving time forward (sec.): 24.8
GRK average driving time forward (sec.): 5.0
GRK total driving time reverse (sec.): 17.7
GRK average driving time reverse (sec.): 3.5

The 2551-20 isn’t designed for driving big structural screws and lag bolts, as demonstrated by its lagging performance in our GRK speed tests designed to test brute force. However, when put up against 12V impact drivers, the 2551-20 shines in these tests.

It’s also an extremely capable impact driver for its intended usage, primarily driving screws 3 inches and shorter. Speed isn’t necessarily crucial in these scenarios. Instead, capable driving power and accuracy prevail. The 2551-20 excels in these lighter and medium-duty jobs, especially with its quiet oil-impulse impact.

Compare driving speed test results

Drive modes

Milwaukee 2551-20 Drive Modes

Drive modes: 4
Drive mode 1:  High speed 
Drive mode 2:  Medium speed 
Drive mode 3:  Low speed 
Drive mode 4:  Self-tapping 
Variable speed trigger: Yes

There are four driving modes on the 2551-20, great for driving versatility. Drive modes we label as 1, 2, 3, and 4 correspond to high speed, medium speed, low speed, and self-tapping screw modes. The advertised impacts per minute for the speed modes are 3400.00, 2200.0, and 950.0, respectively.

Drive mode 1 is ideal for heavier-duty tasks, such as driving lag bolts and decking screws. This mode finishes screws nicely, compared to the brute force high-speed modes on most 18V impact drivers.

Drive mode 2 is the best if you want a clean and consistent screw recess. The mode has enough power to drive screws into dimensional lumber, treated lumber, plywood, and hard and softwood.

We found ourselves favoring drive mode 2 over drive mode 1 since the lower setting lacks power, and drive mode 2 is already highly accurate in all density materials.

The self-tapping mode works well enough driving standard screw sizes in ½-inch to 1-inch lengths in thin sheet metal. In this mode, the collet spins and then stops once a specific light rotational force is reached, then it starts again slowly for a short moment. Holding the trigger repeats the cycle, helpful when the first cycle doesn’t set the screw at full depth. Since the rotational force is so sensitive, this drive mode only works well for niche driving scenarios.

Also, the trigger must be fully pushed. Any shorter trigger draw results in operating in a normal impacting mode.

Collet

Milwaukee 2551-20 Collet Closeup

Collet size: 1/4-inch hex
Quick-change collet: Yes
Bit-eject collet: No
Easy-insert collet: No

Milwaukee rarely includes a bit-eject feature on its impact drivers, but some models have an incredibly smooth easy-insert design, both of which are true with the 2551-20.

Many Dewalt impact drivers include easy-insert and bit-eject collets that are smooth with the best collet design we’ve come across.

Motor

Motor: Brushless
Impacts per minute: 3,400.0

Brushless motors, like the one included in the 2551-20, improve driving efficiency, increase battery run time, and are more durable than their brushed motor counterparts.

Understandably since it’s a hydraulic impact driver, the 2551-20’s advertised 3400.0 impacts per minute are low, explaining some of the slow driving performance in our tests and some of the precision screw finishing as well. Most tools have tradeoffs, and the impacting frequency is worth considering based on your intended usage.

One differentiating factor is that the percussive impact is powered by hydraulic action. The expanding and contracting oil pulses spin the collet, resulting in a less violent and more prolonged impact than traditional hammer-impacting models.

Battery run time

Power type: Cordless
Battery run time (min.): 26.0
Battery tested: 12V Red Lithium CP 2Ah (48-11-2420)
Voltage: 12

One crucial downside is the lacking battery run time performance, which is familiar with several Milwaukee impact drivers.The Makita 12V CXT DT04Z and Dewalt 12V Xtreme DCF801 have much better battery life.

We tested battery run time with the 2Ah battery version. With an M12 5Ah battery, expect the battery run time to increase but continue underperforming competing models running the same Ah setup.

Compare battery test results

Charging time

Milwaukee 2551-20 Fuel Gauge

Charger tested: Milwaukee M12 & M18 Multi-Volt (48-59-1812)
Charging time 2Ah battery (min.): 38.0
Charging time 2.5Ah battery (min.): Not tested
Charging time 4Ah battery (min.): Not tested
Charging time 5Ah battery (min.): Not tested
Charging time per Ah (min.): 19.0
Fuel gauge: Onboard tool

The Milwaukee M12 and M18 multi-volt charger (model 48-59-1812) included in most kits is reasonably fast at charging batteries, including to beat out team red’s most frequent adversary, Dewalt. It takes 38 minutes to charge an M12 2Ah battery, or 19 minutes per amp-hour.

Milwaukee’s 48-59-1812 charger charges multiple battery voltages in one, conveniently saving space in your shop if you have several M12 and M18 ecosystem tools.

Compare charging test results

Design & ergonomics

Stands upright w/o battery: No
Stands upright w/ battery: Yes
Grip material: Rubber overgrip
Magnetic holder: No
Bit holder: No
Belt hook: Yes
Handle angle (deg.): 90.0
Head angle (deg.): 103.0

Weight

Milwaukee 2551-20 On Scale

Bare weight (lbs): 2.02
Weight w/ 2Ah battery (lbs): 2.41
Weight w/ 2.5Ah battery (lbs):  Not tested
Weight w/ 4Ah battery (lbs):  Not tested
Weight w/ 5Ah battery (lbs): Not tested

The 2551-20 is moderately heavy for a 12V impact driver in its bare form and with a battery but is lightweight compared to most 18V impact drivers, helping to reduce muscle fatigue.

The working weight can differ significantly depending on the battery run in your setup. To keep it lightweight, we recommend combining the 2551-20 with Milwaukee’s M12 Red Lithium CP 2Ah battery for a good balance of performance and weight.

If weight is less of a concern, Milwaukee offers several higher Ah M12 batteries in its lineup. However, you forego the in-handle design for a slightly bulkier footprint and weight. Upgrading to Milwaukee’s M18 lineup may be more suitable as the size increases.

Compare weight test results

Footprint

Milwaukee 2551-20 Size

Max height (bare tool, in.): 7.000
Max width (bare tool, in.): 2.375
Collet to back length (in.): 5.125
Base length (bare tool, in.): 1.625
Base width (bare tool, in.): 1.625
Trigger circumference (in.): 6.500
Handle circumference (in.): 6.250

The 2551-20 is highly compact with its low max width and relatively short collet-to-back length. The size helps it fit nicely into tight corners and openings.

Compare footprint test results

Driving clearance

Min. interior width clearance (in.): 7.750
Min. top edge clearance (in.): 1.125
Min. interior 45-deg. clearance (in.): 6.250

The 2551-20 performed moderately well in our clearance tests due to its compact, short collet-to-back footprint, making it suitable for fitting in tight spaces and openings. Compared to more traditionally-designed models, the in-handle battery design also improves its clearance performance.

The Milwaukee M18 Fuel 3453-20 shined in our clearance tests, primarily due to its stubbier collet-to-back length.

Compare driving clearance test results

Noise

2551-20 Impact Driver Noise Chart

Max noise no load (dBA): 87.7
Max impacting noise (dBA): 86.1

The 2551-20 is a dream regarding its noise performance, which is one of the primary reasons to buy a hydraulic impact driver. The noise when impacting is exceptionally low compared to hammer-based impact driver designs.

The noise performance is most noticeably low when driving standard screw sizes and lengths under 3 inches. The 2551-20 is as close to whispering as you’ll get with an impact driver. We measured as low as 84.3 dBA impacting short screws, approximating an airplane’s inside ambient noise.

Consider the Milwaukee M18 Fuel Surge 2760-20 for a more powerful hydraulic impact driver with exceptional noise performance.

Compare noise test results

Vibration

Max head vibration no load (m/s2): 21.2
Max grip vibration no load (m/s2): 1.2

Grip vibration is incredibly low with the 2551-20’s less violent and muted oil-impulse impacts, making it ideal if you want an easy-to-handle impact driver.

Compare vibration test results

Light

Milwaukee 2551-20 Light
Milwaukee 2551-20 Light Closeup

Light: Yes
Light on/off: No
Number of lights: 1
Light time delay (sec.): 10.0

The work light brightly illuminates a moderately large work area. The work light can’t be disabled and doesn’t act as a dedicated flashlight.

Several Makita impact drivers include a dedicated flashlight functionally with the forward/reverse switch set to neutral.

Warranty

Tool warranty (years): 5
Battery warranty (years): 2-3 (depends on model)

Milwaukee stands behind the durability of its drills with exceptionally long warranties. The 2551-20 has a five-year warranty, which is among the longest offered by any manufacturer. Milwaukee’s M12 Li-Ion batteries have two or three-year warranties, depending on the specific model.

Nathan Hamilton
Nathan Hamilton
Nathan Hamilton is the founder of DIY Gear Reviews and a recognized expert in the home and DIY space. He has over 200 bylines covering topics such as power tools, hand tools, and woodworking. Nathan is the strategic director for DIY Gear Reviews, deciding everything from the content covered to designing the testing methodologies for lab-tested reviews. He can be emailed at nhamilton@diygearreviews.com.

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