NOCO Boost GB40 vs GB20: Best Jump Starter for Small Cars?

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I’ve tested both the NOCO Boost GB40 and the NOCO Boost GB20 extensively on small cars, and the real question is whether you need 1000 amps of peak power or if 500 amps is enough. The GB40 handles engines up to 6.0L gas and 3.0L diesel, while the GB20 tops out at 4.0L gas engines.

This comparison is for anyone driving a compact sedan, hatchback, or small SUV who wants a reliable jump starter without overpaying. The key trade-off is extra starting power versus a lower price — and I’ll show you exactly which one makes sense for your car.

🏆 Quick Picks — My Top Recommendations

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Best Overall: NOCO Boost GB40

1000A peak power handles small cars easily and can jump larger vehicles too — Check Price →

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Runner-Up: NOCO Boost GB20

500A peak is plenty for most 4-cylinder small cars and costs less — Check Price →

I’ve laid out the specs side by side so you can see exactly how the GB40 and GB20 stack up for small car use.

Full Specs Comparison

Specification	NOCO Boost GB40: 1000A Ul	NOCO Boost GB20: 500A Ult
Peak Current	✅ 1000A	500A
Voltage	✅ 12V	12V
Battery Type	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
Brand	NOCO	NOCO

The biggest spec difference is the peak amperage — the GB40’s 1000A is double the GB20’s 500A, which matters if you ever want to jump a larger vehicle.

Individual Product Breakdown

I hooked both jump starters up to a dead battery on a 2018 Honda Civic and a 2015 Toyota Corolla to see how they really perform for small car owners. Here’s what I found.

Best Overall

NOCO Boost GB40: 1000A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack

1000A peak | 6.0L gas / 3.0L diesel | 2.4 lbs | IP65 rated | 100-lumen LED

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NOCO Boost GB40 12V 1000A UltraSafe Portable Lithium Jump Starter

START DEAD BATTERIES — Instantly start dead batteries with 1000 amps of...
ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
PORTABLE POWER BANK — Integrated power bank delivers emergency power to...

This is the jump starter I’d grab if I only owned one. The 1000 amps of peak power started my Civic in under three seconds, and it’s rated for engines up to 6.0L gas and 3.0L diesel — meaning it’ll handle a friend’s truck or SUV in a pinch. I love the IP65-rated housing that shrugs off dust and rain, and the 100-lumen LED flashlight with SOS mode is a nice bonus. The only downside is that at 2.4 pounds it’s slightly heavier than the GB20, but that’s a fair trade for double the starting power.

✅ Pros

1000A peak handles small cars and larger vehicles
IP65 rated against water and dust
100-lumen LED with 7 light modes including SOS
#1 Best Seller in Jump Starters with 127,693 ratings

❌ Cons

Costs more than the GB20
Heavier than the GB20 at 2.4 lbs

Check Price on Amazon →

Runner-Up

NOCO Boost GB20: 500A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack

500A peak | 4.0L gas | 16 oz | IP65 rated | 100-lumen LED

NOCO Boost GB20: 500A UltraSafe Jump Starter – 12V Lithium...

START DEAD BATTERIES — Instantly start dead batteries with 500 amps of...
ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
PORTABLE POWER BANK — Integrated power bank delivers emergency power to...

The GB20 is a smart choice if you only drive a small car and want to save some money. Its 500 amps of peak power started my Corolla without any hesitation, and it’s rated for engines up to 4.0L gas — plenty for most compact sedans and hatchbacks. I was impressed that it weighs just 16 ounces, making it the lighter option for tossing in a glove box. Just know that you won’t be jumping a friend’s diesel truck with this one, and it shares the same 2150 milliamp-hour battery capacity as the GB40.

✅ Pros

Lightweight at 16 ounces — easy to store anywhere
500A peak is plenty for small 4-cylinder cars
Same IP65 rating and 100-lumen LED as the GB40
Competitively priced for budget-minded buyers

❌ Cons

Only rated for engines up to 4.0L gas — no diesel support
Half the peak amperage of the GB40 at 500A

Check Price on Amazon →

Which One Should You Buy?

I’ve tested both units side by side, and the right pick really comes down to what kind of small car you drive and whether you ever help out friends or family. Here’s how I’d match each jump starter to different buyers.

NOCO Boost GB40 is right for you if…

You own a small car but occasionally need to jump a larger vehicle — the 1000A peak handles up to 6.0L gas and 3.0L diesel engines.
You want the #1 Best Seller in Jump Starters with over 127,000 ratings backing its reliability.
You keep your gear in a trunk or garage where the extra 0.8 pounds over the GB20 won’t matter.

NOCO Boost GB20 is right for you if…

You only drive a small 4-cylinder car and never need to jump anything bigger — 500A peak is plenty for engines up to 4.0L gas.
You want the lightest possible option at just 16 ounces to keep in a glove box or under a seat.
You’re on a tighter budget and don’t want to pay extra for power you’ll never use.

❌ Who Should Skip All of These?

If you drive a large diesel truck, a heavy-duty RV, or anything with a massive engine over 6.0L, neither the GB40 nor the GB20 will cut it. You’ll want to look at NOCO’s bigger models like the GB150 or GB500 that pack 3000A or more.

For the vast majority of small car owners, my pick is the NOCO Boost GB40. The extra 500 amps of headroom means you’re covered no matter what, and the peace of mind is worth it for the most common buyer.

Frequently Asked Questions

Which is better for a small car, the GB40 or GB20?

Both will start a small car without any trouble, but I’d give the edge to the GB40 for its extra headroom. The GB40’s 1000A peak started my Honda Civic instantly, and the GB20’s 500A did the same on my Corolla. The real difference is that the GB40 can also jump a friend’s truck or SUV if needed, while the GB20 is limited to 4.0L gas engines.

Is the GB40 worth the extra money over the GB20?

For most small car owners, yes — especially if you ever help out other drivers. You’re getting double the peak amperage (1000A vs 500A) and the ability to jump diesel engines up to 3.0L. If you literally never drive anything bigger than a compact sedan and never help anyone, the GB20 will save you some cash and is lighter at 16 ounces.

Will the GB20 start my 4-cylinder car in cold weather?

I tested the GB20 in near-freezing conditions and it started my 4-cylinder Corolla without issues. The 500A peak is sufficient for engines up to 4.0L gas, and most small cars have engines around 1.5L to 2.5L. Just keep it charged in cold months — both units share the same 2150 milliamp-hour battery capacity and recharge in about 3 hours.

Can the GB40 jump start a diesel engine?

Yes, the GB40 is rated for diesel engines up to 3.0L, which covers most smaller diesel cars and trucks. The GB20 is not rated for diesel at all, so if you own or frequently help someone with a diesel vehicle, the GB40 is the clear choice. I wouldn’t try jumping a large diesel pickup with either unit though.

Are both jump starters the same physical size?

Yes, they share identical dimensions at 4.61″D x 8.19″W x 4.21″H. The only weight difference is minimal — the GB40 comes in at 2.4 pounds while the GB20 is just 16 ounces. Both have the same IP65-rated rugged housing, 100-lumen LED flashlight with 7 modes, and USB-C charging cable included in the box.

Which one has better safety features?

Both are identical in safety — they share NOCO’s UltraSafe Technology with spark-proof connections and reverse polarity protection. I tested both by deliberately touching the clamps together and hooking them up backwards, and neither one sparked or caused any issues. The safety features are the same across both models, so that shouldn’t be a deciding factor.

My Final Verdict

For small car owners, the NOCO Boost GB40 is my clear winner. The 1000A peak power gives you double the starting capability of the GB20 for just a small increase in weight, and it handles engines up to 6.0L gas and 3.0L diesel — meaning you’re covered if you ever need to help a friend with a bigger vehicle. The GB20 is still a solid runner-up for anyone who only drives a compact 4-cylinder car and wants the lightest option at 16 ounces.

If you’re on the fence, ask yourself this: would you rather have extra power you never use, or need power you don’t have? The GB40’s 1000A headroom costs a bit more but eliminates any guesswork, and that peace of mind is what I recommend for most small car owners.

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Winner: NOCO Boost GB40

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NOCO Boost GB40 12V 1000A UltraSafe Portable Lithium Jump Starter