Best Spark Plugs

Don’t let their small size fool you—spark plugs emit an electrical spark across a tiny gap to ignite the combustion required to start your vehicle.

By setting your motor’s pistons in motion, your ride can roar to life, stay running, and deliver a smooth burn of the compressed air-fuel mixture. Is your engine due for a spark plug replacement? Join us as we explore the best spark plugs that keep your engine going strong.

Benefits of Spark Plugs

  • Increase fuel efficiency. If your engine is powered by worn-out spark plugs, it will not run as efficiently as intended. When you replace these faulty plugs with a set of fresh plugs, your engine will run smoothly and require less effort to keep the combustion process going. This will translate into increased fuel efficiency over the long run.
  • Improve acceleration and engine response. If you notice that your ride isn’t as peppy as it usually is when you step on the gas pedal, you may need to replace your spark plugs. Healthy spark plugs maximize the combustion process in your engine, giving you smooth, responsive acceleration.
  • Smoother engine idle. Fully functioning spark plugs provide sufficient ignition to spur the combustion process in your motor. When spark plugs become faulty, they cause your engine to run rougher than usual, which results in symptoms such as a rough idle. Replacing tired plugs with a set of new plugs will smooth out your idle.
  • Reduce the risk of damage to your engine and other components. Faulty spark plugs can cause misfires, poor fuel economy, lackluster acceleration, and other issues with your ignition system. Left unaddressed, malfunctioning plugs can also cause damage to other components such as your catalytic converter, so it’s vital that you immediately replace bad plugs.
  • Enhanced reliability. If you’re experiencing difficulties starting your car, truck, or SUV, your spark plugs may need to be replaced. Spark plugs are a crucial electrical component necessary to start your vehicle, so inspect your plugs if you’re having trouble getting your ride running.

Types of Spark Plugs


Copper core spark plugs are the most basic and affordable type of spark plug that you can buy. These used to be the most common plug type on the market, but have recently been replaced by platinum and iridium spark plugs due to their superior performance, efficiency, and lifespan. While many modern engines simply cannot run copper spark plugs, there are a number of older engines that run better using copper plugs. 


Platinum plugs deliver enhanced performance and fuel efficiency compared to copper plugs, but for a considerably cheaper price than iridium spark plugs. Much like iridium plugs, platinum spark plugs operate at a lower temperature than copper spark plugs. They can also last up to twice as long as basic copper plugs.


Double-platinum spark plugs provide even more performance, efficiency, and longevity than single-plated platinum plugs. What’s more, double-platinum plugs are still typically cheaper than iridium spark plugs. For an affordable upgrade from single platinum, just look for spark plugs that use platinum in both the electrode and cap.


The best spark plugs on the market boast an iridium construction. Iridium spark plugs give you even better gas mileage, performance, reliability, and longevity than double-platinum plugs. Due to the advanced material and innovative technology integrated into iridium spark plugs, these plugs are priced higher than copper and platinum options. Iridium spark plugs are perfect to use on high-performance engines.

Top Brands


Founded in 1916, ACDelco is a Grand Blanc, Michigan-based automotive parts brand owned by General Motors. Offering everything from air conditioning components to batteries, ACDelco is perhaps best known for its line of spark plugs. One of its top products is the ACDelco 41-993 Professional Iridium Spark Plug. 


Established in 1886, Robert Bosch GmbH, or simply Bosch, is a massive multinational engineering and electronics company with its headquarters near Stuttgart, Germany. Bosch manufactures a vast diversity of goods, from home appliances to auto parts. One of its best-selling products is the Bosch 6702 Platinum Spark Plug. 


Operating from Nagoya, Japan, NGK Spark Plug Co., Ltd. is a public company tracing its roots back to 1936. NGK is best known for its range of spark plugs, though it also manufactures fine ceramics, cutting tools, and more. One of this brand’s popular products is its 6619 Iridium IX Spark Plug.

Key Features


When you’re shopping for spark plugs, it’s important to consider which material best suits your needs. Copper is ideal for older model vehicles that feature a low-voltage distributor-based ignition. Platinum and iridium are best suited for modern engines without distributors. Platinum delivers a great mix of economy, performance, and longevity. Iridium offers an even better mix but at a higher cost. In the end, always use the plug specified by your vehicle’s manufacturer.


One important way that spark plugs are specified is by the size of the thread or nut. In the United States, typical thread and nut sizes are as follows: 10mm (nut: 16mm), 12mm (nut: 14mm, 16mm, or 17.5mm), 14mm (nut: 16mm or 20.63mm), and 18mm (nut: 20.63mm). 


A spark plug is specified as “hot” if it’s a better heat insulator, and it’s classified as “cold” if it can conduct more heat out of the tip and lower its temperature. Generally, manufacturers denote the heat range of a spark plug with a number, with some brands using ascending numbers for hotter plugs and others doing the opposite for colder spark plugs.


Spark plugs are usually engineered to have a spark gap which can be adjusted using a spark plug gapper tool. A single plug may be designed for several different engines, necessitating a different gap for each. Spark plugs for cars typically gap between 0.6 and 1.8mm (0.024 and 0.071 inches). Use a gap gauge to measure the plug’s gap to ensure that it’s within the specified range. 

Other Considerations

  • User-Friendliness: Some spark plugs come “pre-gapped” right out of the box and does not require adjustment. These pre-gapped spark plugs are convenient and ideal for consumers looking for a plug-and-play style plug that doesn’t require fussing with a gap gauge and tool during installation. If you have some experience turning a wrench, this may not be a huge deal though.  

Best Spark Plugs You Can Buy Online

1. NGK 6619 Iridium IX Spark Plugs

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The NGK 6619 Iridium IX Spark Plugs snags the top pick in our spark plug comparison because they offer the best mix of high-performance, fuel efficiency, durability, and dependability.

Featuring an iridium construction, these high-quality spark plugs provide a longer lifespan than copper and platinum spark plugs.

Their ultra-fine electrode wire promises superior fuel efficiency as well as silky-smooth engine idle and response. You can also expect a healthy boost in power and torque thanks to the optimal air-fuel mixture that these iridium spark plugs generate.

They receive top marks for durability with such impressive features as metal plating to resist corrosion and seizing, as well as a long insulator nose to prevent fouling. 

We were hard pressed to come up with any cons for these spark plugs, but if we had to ding them for something, it would be their rather expensive price per spark plug. This higher price may seem like a big ask for more frugal motorists, but the exquisite quality and peerless performance that the NGK 6619 spark plugs deliver make them well worth their cost.

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2. Denso 4504 PK20TT Platinum Spark Plugs

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If you’re in the market for solid all-around spark plugs that are easy on your wallet, look no further than the Denso 4504 PK20TT Platinum Spark Plugs. These value-priced platinum plugs pack a whole lot of performance, efficiency, and durability for a downright reasonable price.

Featuring a dual-platinum construction with a platinum disc and platinum electrode tip, these spark plugs provide a reliable spark to generate smooth, reliable combustion of the air-fuel mixture. This translates to great engine dependability, fuel efficiency, and performance.

Another impressive feature is purified alumina powder, which is used as an insulator to increase thermal conductivity for maximum longevity. 

However, there are a few faults that we found with these double-platinum spark plugs. Occasionally, the gap is incorrectly set on some of the plugs. This is why it’s critical that you inspect the gap and adjust it accordingly.

In addition, these double-platinum plugs cannot match the quality, performance, and longevity that iridium spark plugs boast. Nonetheless, we believe that Denso 4504 PK20TT Platinum Spark Plugs are some of the best affordable spark plugs for your car, truck, or SUV. 

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3. Bosch ZGR6STE2 Copper with Nickel Spark Plug

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To boost cold starts and enhance fuel ignition, these spark plugs feature a nickel-chromium ground electrode. They have heavy-duty yttrium enhanced copper core center for optimum performance, reliability, and heat transfer.

These plugs are very durable and have a long lifespan. The nickel-plated shell provides anti-seize and corrosion protection. No gapping is required, and the plug’s ribbed insulator prevents flashover.

The plugs remedy misfires in certain vehicles, can increase mileage in some vehicles, and may boost performance by a noticeable amount.

One issue with these plugs is they may not fit certain vehicles even though the specs indicate that they will. They may also be shipped in non-padded boxes with the plugs rolling around loosely in the package, which could damage them.

Another problem is while the gap is set at the factory, they still may need to be slightly adjusted.

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4. Bosch X5DC Copper with Nickel Spark Plug

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This OE replacement plug has a long lifespan and is very durable. The iridium firing pin is welded with a 360-degree continuous laser, and the copper core is designed to reduce fouling. 

The wire is ultra-fine, and the nickel-plated shell prevents it from seizing. No gapping is required, and the plug has corrosion protection.

One of the best things about these plugs is they last a long time, which is important if you have an engine in which the plugs are difficult to access. While you may not notice a change in mileage after you install them, you may see a boost in performance.

They are also very reliable, and you don’t need a special gap tool for installation.

However, they are not compatible with all vehicles, so you need to double-check the gap to see if they will fit your make and model.

Also, there have been some complaints that the boxes get damaged during shipping, and the plugs roll around loosely, which can potentially damage them.

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5. NGK 4929 Standard Spark Plug

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The NGK 4929 spark plug for motorcycles and UTVs has a solid copper core for more spark and a long insulator nose to minimize fouling. It’s dipped in zinc to prevent corrosion and features insulators with corrugated ribs to reduce flashover.

To eliminate gas leakage, the plug has a triple gasket seal.

These plugs work well on a variety of bikes, including Suzukis, Triumphs, and Honda Recon 250s, among others.

They work as expected and keep your bike running well in temperatures as low as 24-degrees Fahrenheit or as high as 100-degrees Fahrenheit. Overall, they have clean, crisp threads and are easy to install.

However, they won’t fit on all bike models. Also, while they’re a decent price, you may be able to find a cheaper alternative. In addition, the plugs don’t come with screw-on caps, which you may need for certain applications.

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6. NGK BKR7EIX Iridium IX Spark Plug

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NGK’s Iridium IX spark plug is designed to boost throttle response and prevent fouling.

Since iridium alloy has a high melting point, the plug is ideal for high-performance engines. It features a 0.6mm laser-welded fine iridium tip for a longer lifespan and a stable spark. It’s designed to reduce and prevent flashover, combustion gas leakage, and electrical quenching. 

The plugs have anti-corrosion and anti-seizing characteristics. It’s common for a vehicle to exhibit an improvement in acceleration and a slight increase in gas mileage after installing these plugs.

They are simple to install, and your vehicle will run smoother and more efficiently. Overall, they’re great for turbocharged and supercharged cars.

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7. E3.36 Power Sport Spark Plug

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These racing spark plugs are designed to boost fuel economy, provide smooth acceleration, and enable quick starts.

They are leakproof and feature a 100 percent copper core for durability and to improve heat transfer. They have multi-rib insulators to prevent misfires and are designed to work with performance modifications.

Your bike will start quicker and will run noticeably better once you install these plugs. They give your bike a boost of power and provide good gas mileage. Overall, your bike will feel more responsive. In addition, you can use these plugs in lawnmowers, leaf blowers, generators, and ATVs.

However, there have been some complaints that these plugs are a little overpriced and that there is little difference in performance compared to some brands of iridium plugs, such as NGK.

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Spark Plugs – Frequently Asked Questions


A: In typical driving circumstances, you should use the spark plugs specified by your vehicle’s manufacturer. A hot plug may be a good option if your spark plugs are fouled from carbon deposits, your engine has a rich air-fuel ratio or burns oil, or if you do a lot of local low-speed driving. If your engine is pinging, has a lean air-fuel ratio, or if you do a lot of high-speed driving, consider a cold plug.


A: This depends on the quality of spark plugs you have in your car. Top-quality spark plugs will last longer than lower-quality plugs. Most mechanics recommend you change your copper core spark plugs every 30,000 miles or every 50,000 miles for iridium core spark plugs. This interval may be shorter if your engine isn’t in top condition, so it’s vital to inspect your spark plugs for premature wear and change them accordingly.


A: You may notice the following symptoms if your spark plugs need to be replaced: hesitation or backfiring during acceleration, decreased acceleration, rough idle, spark plug wires charred on the end that goes onto the plugs, a significant drop in fuel economy, and difficulties starting your engine. If your ride doesn’t run as well as it usually does, and you suspect it’s attributed to bad spark plugs, inspect the plugs yourself or have a mechanic do it.


A: Yes, you can clean your spark plugs, but it’s generally not recommended. When you clean a spark plug using a wire brush or sturdy knife to scrape off the deposits, it can dull it and drastically lower its efficiency. If you insist on cleaning your spark plugs, use a spray-on plug cleaner specifically engineered for this vital component. 


A: As long as unopened spark plugs are properly stored in a dry, cool environment, then they should last an indefinite amount of time. The lifespan of spark plugs is impacted only when they are exposed to corrosive environmental factors such as moisture or if they’re dropped frequently.

Final Thoughts

Our first place pick for the best spark plugs on the market is the NGK 6619 Iridium IX. These iridium plugs will deliver unbeatable engine performance, fuel efficiency, longevity, and protection from misfires and malfunctions.

If you’re looking for value-priced plugs offering some serious performance, the Denso 4504 PK20TT Platinum Spark Plugs will do nicely.






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