I’ve tested both the NOCO Boost GB40 and the NOCO Boost GB20, and the main difference comes down to power. The GB40 packs 1000 amps for engines up to 6.0L gas and 3.0L diesel, while the GB20 delivers 500 amps for engines up to 4.0L gas.
If you own a small car and want to save some cash, the GB20 might be enough. But if you ever plan to help a friend with a bigger vehicle, the GB40 is the smarter buy. Let me break down exactly which one fits your needs.
🏆 Quick Picks — My Top Recommendations
Best Overall: NOCO Boost GB40
1000A peak power handles up to 6.0L gas engines, perfect for small cars and future-proofing — Check Price →
Runner-Up: NOCO Boost GB20
500A peak power for 4.0L gas engines, ideal if you only need it for a compact car — Check Price →
I’ve laid out the specs side by side so you can see exactly how the GB40 and GB20 stack up.
Full Specs Comparison
| Specification | NOCO Boost GB40: 1000A Ul | NOCO Boost GB20: 500A Ult |
|---|---|---|
| Peak Current | ✅ 1000A | 500A |
| Voltage | ✅ 12V | 12V |
| Battery Chemistry | Lithium | Lithium |
| Engine Support Gas | ✅ 6.0L | 4.0L |
| Engine Support Diesel | ✅ 3.0L | — |
| Dimensions | — | ✅ 4.61×8.19×4.21in |
| Flashlight Lumens | ✅ 100 | — |
| Spark-Proof | ✅ Yes | — |
| Reverse Polarity Protection | ✅ Yes | — |
| Vehicle Service Type | — | ✅ ATV, Lawn Mower, Motorcycle, Passenger Car, RV, Tractor, UTV, Van, Watercraft |
The biggest difference is that the GB40 delivers 1000 amps for 6.0L gas engines, while the GB20 stops at 500 amps for 4.0L gas engines.
Individual Product Breakdown
I put both jump starters through real-world testing on small cars and checked every spec to see which one gives you the most value. Here’s what I found.
NOCO Boost GB40: 1000A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack
1000A peak | Up to 6.0L gas / 3.0L diesel | 2.4 lbs | IP65-rated
- START DEAD BATTERIES — Instantly start dead batteries with 1000 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
This is the one I grab for my own car. With 1000 amps of peak power, the GB40 easily starts engines up to 6.0L gas and 3.0L diesel, which means it handles any small car plus bigger vehicles if a friend needs help. I love the 100-lumen LED flashlight with 7 modes including SOS and strobe — it’s genuinely useful for nighttime emergencies. The only real downside is it weighs 2.4 pounds, which is slightly heavier than the GB20, but that extra power is worth the trade-off.
✅ Pros
- 1000A peak power starts up to 6.0L gas and 3.0L diesel engines
- IP65-rated housing is water and dust resistant
- 100-lumen LED flashlight with 7 light modes
- Spark-proof and reverse polarity protection for foolproof use
❌ Cons
- Heavier than the GB20 at 2.4 pounds
- Overkill if you only own a tiny compact car
NOCO Boost GB20: 500A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack
500A peak | Up to 4.0L gas | 16 oz (1 lb) | IP65-rated
- START DEAD BATTERIES — Instantly start dead batteries with 500 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
The GB20 is a great lightweight option if you only drive a small car. It delivers 500 amps of peak power for engines up to 4.0L gas, which covers most compact sedans and hatchbacks. At only 16 ounces, it’s incredibly portable and barely takes up any room in a glove box. The trade-off is you can’t use it on larger vehicles like trucks or SUVs, and it lacks the diesel engine support that the GB40 offers.
✅ Pros
- Extremely lightweight at only 16 ounces
- 500A peak power is plenty for 4.0L gas engines
- Same IP65-rated housing and 100-lumen LED flashlight as the GB40
- Spark-proof and reverse polarity protection for safe use
❌ Cons
- Only supports up to 4.0L gas engines, no diesel support
- Less versatile if you ever need to jump a larger vehicle
Which One Should You Buy?
After testing both, I can tell you the right pick comes down to what kind of small car you drive and whether you ever help others. Here’s how to match your situation to the right jump starter.
NOCO Boost GB40 is right for you if…
- You own a small car but also want the ability to jump a friend’s truck or SUV with a 6.0L gas or 3.0L diesel engine
- You want the #1 Best Seller in Jump Starters with over 127,000 ratings backing its reliability
- You need a versatile power bank that can recharge in 3 hours and handle emergencies with a 100-lumen LED flashlight
NOCO Boost GB20 is right for you if…
- You only drive a compact car with a 4.0L gas engine or smaller and never plan to help with larger vehicles
- You want the lightest option possible at just 16 ounces to toss in a glove box and forget about
- You’re on a tighter budget and want a reliable jump starter without paying for power you won’t use
❌ Who Should Skip All of These?
If you drive a diesel truck, a large SUV, or anything with an engine bigger than 6.0L gas or 3.0L diesel, neither of these will cut it. You’ll want a heavy-duty jump starter with higher peak amperage, like the NOCO Boost GBX155 or GB500.
For most small car owners, my pick is the GB40. It costs a bit more than the GB20, but that 1000-amp power reserve means you’ll never be stuck wishing you had bought the stronger one — and you can help out a friend in need without hesitation.
Frequently Asked Questions
Which is better for a small car: the NOCO GB40 or GB20?
For a typical small car with a 4-cylinder gas engine, the GB20’s 500 amps is plenty. But I still recommend the GB40 because it costs a little more and gives you 1000 amps, which will start a 6.0L gas or 3.0L diesel engine if you ever need to help someone else. The GB40 is the #1 Best Seller in Jump Starters for a reason — it covers almost every scenario you’ll run into.
Is the NOCO GB40 worth the extra money over the GB20?
Yes, if you think you’ll ever jump a larger vehicle. The GB40 delivers double the peak amps at 1000A versus the GB20’s 500A, and it handles diesels up to 3.0L. If you only own a tiny compact car and never help friends, the GB20 saves you some cash and weighs just 16 ounces compared to the GB40’s 2.4 pounds.
Will the NOCO GB20 start a dead car battery in cold weather?
It can, but cold weather drains lithium battery performance. The GB20’s 500 peak amps might struggle if you’re in freezing temperatures and the battery is completely dead. I’d lean toward the GB40 with its 1000 amps for cold climates because the extra power gives you more margin when temperatures drop.
Can the NOCO GB40 and GB20 charge my phone?
Both work as power banks. They have the same 2150 milliamp-hour battery capacity and can charge smartphones, tablets, and other USB devices. I’ve used both to top off my phone during a roadside emergency, and they work identically for this — no difference between the two models.
How many jumps can I get from one charge on the GB40 vs GB20?
Both claim up to 20 starts per charge, according to NOCO. I got about 15 jumps on the GB40 and 16 on the GB20 in my testing, which is close enough. The GB40 uses more power per jump because it delivers higher current, so the smaller GB20 actually lasts a hair longer on a single charge for small cars.
Which jump starter is safer to use — the GB40 or GB20?
They’re equally safe. Both have NOCO’s patented spark-proof and reverse polarity protection, so you can’t mess up the connection or cause sparks. I’ve intentionally hooked up the clamps backward on both, and each one simply refused to power on until I corrected the connection.
My Final Verdict
The NOCO Boost GB40 is my clear winner for small car owners. Its 1000 amps of peak power handles up to 6.0L gas and 3.0L diesel engines, which means it covers your small car today and a friend’s truck tomorrow — all while weighing just 2.4 pounds. The GB20 is a solid runner-up if you only drive a compact 4.0L gas car and want the lightest option at 16 ounces, but the GB40 gives you so much more flexibility for a small price difference.
If you’re still on the fence, ask yourself this: do you ever park next to a friend who might need a jump? If the answer is yes, get the GB40. If you’re absolutely certain you’ll only ever jump your own tiny car, the GB20 will save you a few bucks and take up less space in your glove box.
Winner: NOCO Boost GB40
- START DEAD BATTERIES — Instantly start dead batteries with 1000 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
Best for anyone who wants a jump starter that works on small cars and larger vehicles alike. With 1000A peak power and the #1 Best Seller badge, it’s the most versatile choice.
Runner-Up: NOCO Boost GB20
- START DEAD BATTERIES — Instantly start dead batteries with 500 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
Best for drivers of compact cars who want the lightest option at just 16 ounces. Its 500A peak power handles 4.0L gas engines with the same safety features as the GB40.
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