Intro
Not every bolt that needs loosening is a massive wheel nut on a tractor. Under the bonnet, inside wheel arches, and tucked behind engine components are hundreds of smaller fasteners — 10 mm, 12 mm, 14 mm bolts — that a full-size 1/2-inch impact wrench is simply too big to reach. That is where a compact 3/8-inch drive impact wrench earns its place. It is lighter, shorter, and far more manoeuvrable than its bigger cousins, letting you get into the tight spaces that define modern engine bays. The reduced size does not mean reduced power — modern brushless motors and lithium-ion batteries pack serious torque into tools that fit in the palm of your hand. For brake caliper bolts, engine cover fasteners, belt tensioners, and suspension hardware in confined spaces, a compact impact wrench is the tool that saves you from skinned knuckles and the frustration of working with a ratchet in a space where you can barely move your hand.
Generalities
The SKIL PWR CORE 20 IW6739B-00 is a subcompact 3/8-inch brushless impact wrench designed for tight-space automotive and mechanical work. At just over 12 cm in length and barely 1 kg in weight, it is significantly smaller than the 1/2-inch impact wrenches typically used for wheel nuts, yet it still delivers up to 298 Newton metres of breakaway torque and 230 Nm of fastening torque. The 3/8-inch square drive accepts a wide range of compact impact sockets, and the friction ring anvil makes socket changes fast and secure. Part of SKIL's PWR CORE 20 battery platform, this is a bare tool sold without a battery or charger, designed for users already invested in the SKIL cordless ecosystem. The brushless digital motor combined with three speed settings provides both high-performance power and precision control.
In this review we will examine the IW6739B-00's real-world performance on the kinds of jobs it was designed for — brake work, engine bay fasteners, and any tight-space bolt that a larger wrench cannot reach. We will assess the effectiveness of the reverse control mode, the Halo Light illumination system, and how the compact size and light weight translate into everyday workshop usability. By the end, you will know whether this subcompact SKIL impact wrench is the right tool for your mechanical toolkit.
Description
The SKIL IW6739B-00 is built around a brushless digital motor running on the PWR CORE 20 battery platform — a 20-volt (nominal 18-volt) system with advanced battery technology that wraps each cell in cooling material for 25% longer runtime and double the battery lifespan compared to standard packs. The motor drives the 3/8-inch square anvil at up to 3,950 impacts per minute, delivering 298 Newton metres of breakaway torque (220 foot-pounds) and 230 Nm of fastening torque (170 foot-pounds). These figures put it in a different class from basic 3/8-inch cordless ratchets — this is a genuine impact wrench capable of removing brake caliper carrier bolts, suspension fasteners, and engine mount bolts. The tool measures approximately 12.2 cm in length and weighs just over 1 kg without a battery, making it over 2.5 cm shorter than the previous generation SKIL compact impact wrench. A belt clip is included for hands-free carrying between tasks.
SKIL has packed thoughtful features into this compact body. The three-speed selector switch lets you choose the right power level for the task: low speed for running fasteners down gently without risk of cross-threading, medium for general assembly work, and high for maximum breakaway torque on stubborn bolts. The reverse control mode is a particularly clever feature — when loosening bolts, the tool automatically reduces speed once the fastener breaks free, preventing it from spinning off at full speed and flying into an inaccessible corner of the engine bay. This saves the maddening experience of hearing a nut or bolt clatter into the undertray or subframe where it takes ten minutes to retrieve. The friction ring anvil holds sockets securely while allowing quick, tool-free changes — push the socket on until it clicks, pull it off when you are done.
The Halo Light is one of the IW6739B-00's most distinctive and genuinely useful features. Rather than a single small LED, SKIL has designed a ring of LEDs around the anvil that provides five times more illumination than standard LED work lights while dramatically reducing shadows. The light stays on for up to 10 minutes after you release the trigger, which means you are not left fumbling in the dark while positioning the socket onto the next bolt. In the cramped, shadowy depths of a wheel arch or engine bay, this level of illumination makes a real difference to both speed and accuracy. In everyday use, the tool's size is its defining advantage. At roughly 12 cm long, it fits into spaces where a 1/2-inch impact wrench — typically 25 to 30 cm — simply cannot go. Brake caliper bolts that are obscured by the suspension strut, belt tensioner bolts buried behind the engine mount, and exhaust manifold nuts tucked against the firewall all become accessible without removing surrounding components to create clearance for a larger tool.
The IW6739B-00 is sold as a bare tool — the package includes the impact wrench body and a belt clip, with no battery or charger. This is the standard approach for cordless tool platforms and makes sense for existing SKIL PWR CORE 20 users who already own compatible batteries. The PWR CORE 20 battery system features proprietary cooling technology that SKIL claims extends both runtime and battery lifespan, and the batteries are interchangeable across the growing range of SKIL 20-volt tools. For optimal performance and runtime, a 4.0 Ah or larger battery is recommended — the 2.0 Ah compact pack will work but runtime drops noticeably under heavy impact use. The tool is compatible with all PWR CORE 20 batteries, so you can use the same packs that power your SKIL drill, circular saw, or other SKIL tools.
The tool measures 12.2 cm in length and weighs approximately 1.01 kg without a battery. With a 4.0 Ah PWR CORE 20 pack fitted, total weight is around 1.7 kg — still light enough for comfortable single-handed use and extended overhead work. SKIL provides their manufacturer warranty, and as part of a well-established brand now owned by Chervon (the same parent company as EGO and Flex), after-sales support across Europe is reasonable. Customer ratings are excellent at 4.7 out of 5 stars, though the review count is low at just 19 — this reflects the tool's relatively recent launch and specialist positioning. The feedback that does exist consistently praises the compact size, the Halo Light effectiveness, and the reverse control mode's practicality. For a subcompact 3/8-inch brushless impact wrench with genuine breakaway torque, the SKIL IW6739B-00 fills a specific but valuable niche in the mechanic's tool collection.
Pros and cons
Pros
- Extremely compact at just 12.2 cm long and barely 1 kg — fits into engine bay spaces and behind suspension components where full-size impact wrenches cannot reach.
- Halo Light ring around the anvil provides 5x more illumination than standard LEDs with reduced shadows — stays on for 10 minutes after trigger release for continuous visibility.
- Reverse control mode automatically slows the tool once a bolt breaks free — prevents fasteners from spinning off and disappearing into the engine bay or undertray.
- 298 Nm breakaway torque from a 3/8-inch tool is impressive — enough for brake caliper bolts, suspension fasteners, and most under-bonnet hardware.
- Three speed settings plus variable trigger — precise control from gentle fastener running to full-power breakaway, with no risk of cross-threading on assembly.
- Part of the SKIL PWR CORE 20 ecosystem — batteries feature cooling technology for extended runtime and lifespan, and are shared across the growing SKIL cordless range.
Cons
- Bare tool only — no battery or charger included, so the effective cost is significantly higher for users not already invested in the SKIL PWR CORE 20 platform.
- 3/8-inch drive limits socket compatibility to smaller sizes — most impact socket sets are 1/2-inch, so you may need to buy a specific 3/8-inch impact socket set.
- Very low review count of just 19 ratings — while the 4.7-star average is excellent, there is limited real-world data on long-term durability and reliability.
- SKIL PWR CORE 20 platform has a smaller tool ecosystem than DEWALT XR, Makita LXT, or Bosch Professional — fewer tools to share batteries with if you are building a comprehensive cordless collection.
Use cases
The SKIL IW6739B-00 is a subcompact 3/8-inch brushless impact wrench for mechanics and serious DIYers who need genuine breakaway torque in the tightest engine bay spaces — with a unique Halo Light, reverse control mode, and the SKIL PWR CORE 20 battery ecosystem.
Brake Caliper and Suspension Fastener Removal
Brake caliper carrier bolts and suspension fasteners are often tucked behind struts, steering knuckles, and heat shields — spaces where a 25 cm long 1/2-inch impact wrench simply will not fit. The IW6739's 12 cm body slides into these gaps, and the 298 Nm breakaway torque cracks even corroded bolts loose. The Halo Light illuminates the work area inside the wheel arch, and the reverse control mode prevents bolts from launching into the undertray.
Under-Bonnet and Engine Bay Fastener Work
Modern engine bays are densely packed — belt tensioners, alternator bolts, intake manifold fasteners, and engine mount hardware are all buried behind hoses, wiring looms, and other components. The IW6739's subcompact size and light weight let you reach these fasteners without the clearance a 1/2-inch tool demands. The three-speed selector ensures you never over-torque delicate aluminium fasteners or plastic-mounted components.
Motorcycle and Powersport Maintenance
Motorcycle engines, ATVs, and personal watercraft have predominantly smaller fasteners — 8, 10, 12, and 14 mm — that are perfectly suited to a 3/8-inch drive impact wrench. The IW6739's compact size fits between frame rails and around fairing mounts without scratching bodywork, and the progressive trigger gives the control needed for aluminium engine cases where over-tightening can strip threads instantly.
Overhead and Extended-Duration Mechanical Work
Working underneath a vehicle on a creeper, or with arms extended into an engine bay, makes tool weight critically important. At just over 1 kg without a battery, the IW6739 can be held one-handed at full stretch without the arm fatigue that a 3 kg 1/2-inch wrench causes. The belt clip lets you secure the tool to your clothing or a pocket while repositioning, keeping both hands free when you need them.
SKIL PWR CORE 20 Ecosystem Expansion
For users already running SKIL PWR CORE 20 batteries for their drill, circular saw, or other SKIL tools, this bare tool adds a specialised compact impact wrench to the collection without needing new batteries or chargers. The PWR CORE 20 batteries' cooling technology provides consistent power delivery during sustained impact use, and the tool's modest power demands mean even a 2.0 Ah compact pack provides useful runtime for intermittent mechanical work.