NOCO Boost GB40 Review: Is It Still the Best Jump Starter for Cars?
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The NOCO Boost GB40 is still one of the best jump starters for everyday cars. It covers gas engines up to 6.0L and diesels up to 3.0L, weighs about 2.5 lb, and its spark-proof, reverse-polarity clamps make it very hard to use wrongly. Buy it for a sedan, hatchback, crossover or V6 SUV. Skip it for a V8 truck or a larger diesel, where the NOCO GB70 is the better fit.
The GB40 has been on the market for years and has become the default answer when someone asks which jump starter to keep in a car. That kind of reputation can hide weaknesses, so this review looks at what the GB40 does well, where newer models have overtaken it, and which drivers should buy something else. We base it on NOCO’s published specs and manual, long-term owner feedback, and how it compares with the other packs in our portable jump starter roundup.
NOCO GB40 Specs at a Glance
| Spec | NOCO Boost GB40 |
|---|---|
| Peak current | 1000A |
| Rated engine size | Gas up to 6.0L, diesel up to 3.0L |
| Starts per charge | Up to 20 (NOCO rating) |
| Recharge time | About 3 hours |
| Safety | Spark-proof, reverse-polarity protection |
| Flashlight | 100 lumens, 7 modes including SOS and strobe |
| Housing | IP65 rated, rubber over-molding |
| Weight | About 2.5 lb |
| Extras | USB power bank for phones and tablets |
NOCO Boost GB40 1000A UltraSafe Lithium Jump Starter
Gas up to 6.0L, diesel up to 3.0L
Check Price on AmazonDesign and Build
The GB40 is a flat, hand-sized brick with a short fixed cable and two compact clamps. It is small enough for a glove box or a seat-back pocket, which is the most important “feature” of any jump pack: the one you leave at home cannot help you. The IP65 rating means the housing resists dust and water jets, so a rainy roadside is not a problem, and the rubber over-molding takes the knocks of rattling around a trunk.
The controls are simple: a power button, a light button, a manual override for very flat batteries, and a row of LEDs for charge level. There is no screen, and for this kind of tool that is not a weakness. Owners who are nervous around car batteries generally find the GB40 easy, because the pack tells you with a light whether the connection is right.
Jump Starting Performance
NOCO rates the GB40 for gas engines up to 6.0L and diesel engines up to 3.0L, with up to 20 starts per charge. In practice that covers almost all four-cylinder and V6 cars, compact and mid-size SUVs, minivans, motorcycles and lawn tractors. Owner feedback is consistent: on a battery that is merely drained (lights left on, car sat for a few weeks) the GB40 starts these vehicles quickly.
Where it struggles is predictable. Large V8s, especially in cold weather, and diesels above 3.0L are outside its rating. It may manage a warm V8 once, but it is not the tool you want to depend on in January. For those engines, look at the GB70 or a larger pack. The rating also assumes a battery that can still accept a charge. If the battery is internally shorted or frozen, no jump pack will help, and you should not try.
Manual override for very dead batteries
Smart clamps only send power when they detect a battery. If the battery is so flat that the GB40 cannot detect it, the manual override forces output. It works, but it also switches off the safety detection for that attempt, so double-check the clamps are on the correct terminals before using it, and follow the manual’s steps exactly.
Safety: The Real Reason to Buy It
NOCO’s UltraSafe design is the strongest argument for the GB40. The clamps are spark-proof and reverse-polarity protected, so if you connect red to negative by mistake, nothing happens instead of a spark or a damaged module. On a modern car that matters a lot, because a reverse connection can damage the body control module, the immobilizer and the keyless entry receiver. That is the kind of problem that turns into a very expensive car that won’t start even though the fob unlocks the doors.
Power Bank and Flashlight
The USB output charges a phone or tablet, which is useful when you are waiting for a tow. It is a basic output, slower than the USB-C Power Delivery on NOCO’s newer Boost X models, and it will not charge a laptop. The 100-lumen LED has seven modes including SOS and strobe. It is bright enough to see the battery terminals, but owners who want a real work light will prefer the 400-lumen light on the GB70.
Charging and Standby
A full recharge takes about three hours. The GB40 uses an older charging port, not USB-C, so keep its cable in the car. Lithium packs slowly lose charge, especially in heat, so the habit that matters most is recharging after every use and every two to three months in storage. If you forget gadgets for months at a time, the GBX45 recharges in about 48 minutes over USB-C, which makes topping up much less of a chore.
What the GB40 Can and Cannot Start
| Vehicle | Typical engine | GB40 suitable? |
|---|---|---|
| Compact car or hatchback | 1.5L to 2.0L 4-cylinder | Yes, with plenty of margin |
| Mid-size sedan | 2.5L 4-cylinder or 3.5L V6 | Yes |
| Compact or mid-size SUV, minivan | 2.0L turbo to 3.6L V6 | Yes |
| Motorcycle, ATV, lawn tractor | Small 12V engines | Yes |
| Half-ton V8 pickup | 5.0L to 6.2L V8 | Borderline, especially in cold weather |
| Light diesel (3.0L) | 3.0L turbo-diesel | At its limit; the GB70 is safer |
| Heavy-duty diesel | 6.6L to 6.7L | No |
Two things move a vehicle toward the “borderline” row: cold temperatures and a battery that is deeply discharged rather than just drained. If either is common where you live, size up.
How to Keep the GB40 Ready
A jump pack that is flat when you need it is the most common failure, and it is avoidable. Recharge the GB40 as soon as you get home after using it, and set a reminder to check it every two to three months, for example when you change the clocks or check tire pressures. In summer, do not leave it on the dashboard or in direct sun, since heat speeds up self-discharge and ages lithium cells. In deep winter, bring it inside the night before a cold start you are worried about. With that routine, owners commonly get many years from one pack.
What Could Be Better
- Older charging connector. USB-C would make it easier to charge from a modern car or phone charger.
- Basic power bank. Fine for a phone, not for a laptop.
- Not for big engines. V8 trucks and diesels above 3.0L need more.
- Dim light compared with larger NOCO packs.
Pros and Cons
Pros: very compact, proven spark-proof and reverse-polarity clamps, IP65 housing, up to 20 starts per charge, simple to use.
Cons: 6.0L gas and 3.0L diesel limit, older charging port, basic USB output and light.
Who Should Buy the NOCO GB40?
Buy it if you drive a 4-cylinder or V6 car, crossover, minivan or small SUV, you want a pack that lives in the glove box, and you value safety over extra features. It is also a sensible gift for a new driver.
Skip it if you drive a V8 pickup, a large SUV or a diesel above 3.0L, or you want a tire inflator in the same box.
NOCO GB40 Alternatives
| If you want… | Consider | Why |
|---|---|---|
| Fast USB-C recharging | NOCO Boost X GBX45 | 48-minute recharge, 60W USB-C, 6.5L gas rating |
| Coverage for V8 trucks | NOCO Boost GB70 | 8.0L gas / 6.0L diesel, 400-lumen light |
| A tire inflator too | GOOLOO A3 | 150 PSI auto-off inflator, 9.0L gas rating |
For a side-by-side breakdown, see NOCO GB40 vs GB70 and NOCO GB40 vs GBX45.
Quick Start: Using the GB40
- Turn off the ignition and all accessories.
- Connect the red clamp to the positive (+) terminal and the black clamp to the negative (-) terminal or bare metal ground.
- Press the power button and wait for the white boost light.
- Start the car. If it does not start, wait about a minute before trying again.
- Remove the clamps (black first), turn the GB40 off and recharge it when you get home.
Our full guide on how to jump start a car covers what to do if the car still will not start.
Related Guides
- 7 best portable jump starters for cars, trucks and SUVs
- Best jump starters with air compressor
- Best jump starters for diesel trucks
- Key fob not detected after a jump start
FAQ
Is the NOCO GB40 enough for a V8?
It is rated for gas engines up to 6.0L, so it covers some smaller V8s, but it has little margin on large V8 trucks, especially in cold weather. The GB70 is the safer choice for V8 pickups.
How long does the NOCO GB40 hold a charge?
A charged GB40 keeps usable power for months, but heat and cold speed up self-discharge. Recharge it after each use and every two to three months in storage.
Can the GB40 jump a completely dead battery?
Yes, using manual override mode, which forces output when the battery is too flat to detect. Check the clamp connections carefully first, because override disables the detection for that attempt.
Can I leave the GB40 in my car?
Yes, that is what it is designed for. Keep it out of direct sun on hot days, and in very cold weather bring it inside the night before you expect to need it.
Will the GB40 damage my car’s electronics?
Used as the manual says, it is very unlikely to. Its spark-proof and reverse-polarity protection prevents the wrong-connection mistakes that cause most electrical damage during jump starts.
Does jump starting reset my key fob?
No, key programming is stored in the car’s modules and is not erased by a jump. If the fob is not detected afterwards, see key fob not detected after a jump start.