6 Best Spark Plugs – (Reviews & Buying Guide 2021)

Is your engine misfiring of late? Does it require an abnormally long ignition to make your gasoline car come to life on cold mornings? Given your presence here, there’s a very good chance that your answer to at least one of these two questions is in the affirmative.

Hence why you could do with the best spark plug on the market. Though tiny in dimensions and meager in their asking price, spark plugs perform the one basic (yet crucial) function without which your car won’t be any good: they ignite its fuel to start combustion.

They provide other benefits as well. A good-quality spark plug can increase your car’s performance, decrease its fuel emissions, and reduce the maintenance costs. You can also count on it to improve your vehicle’s horsepower, which means a trouble-free driving experience on steep roads.

Go through our spark plug reviews to know more.

Best Spark Plug Reviews

1. Bosch X5DC Copper with Nickel Spark Plug

The Bosch X5DC upholds the reputation of its manufacturer that has been churning out spark plugs for a century. It boasts a yttrium enhanced center electrode to lowers the chances of oxidization. Its Ni/Cr ground electrode, meanwhile, improves fuel ignitability and cold starts.

To reduce flashovers and improve the throttle, this unit’s insulator nose is corrugated. You might also find it useful to know that its gaps are set at factory settings. That means that you could simply install this spark plug right out of the box. OEM applications also benefit from its factory set gapping.

You can trust this unit to be anti-seizing as well. The reason for this lies in its nickel-plated shell whose rolled threads keep seizing at bay. Also, thanks to its ultra-fine wiring pin, this spark plug requires less voltage to get your engine up and running.

2. NGK (4929) DPR8EA-9 Standard Spark Plug

Whether you own a high-performance car or an off-road vehicle, the NGK 4929 spark plug will find its place in your vehicle. It boasts a longer-than-usual insulator nose which prevents fouling and keeps engine misfiring and rough idling at bay.

Then come its corrugated ribs which reduce the chances of flashover. The fact that its shell is dipped in zinc means you can count on it to resist corrosion. Also on offer is a triple gasket seal that won’t allow the gas to leak during or after combustion.

Regardless of the voltage coming from behind, the solid copper core of this unit will make sure that the ignitable spark is sent ahead. On top of everything else, this unit is incredibly cheap. So meager is its price tag that you can get three NGK 4929 spark plugs for the price of one Bosch X5DC.

3. E3 Spark Plug E3.36 Powersports Spark Plug

Two standout features of this spark plug set it apart from the competition. It guarantees that whether you run a 2 or 4 stroke engine, the emissions will nosedive about fifty hours after its installation. The time frame is there because the plug requires that duration to come to speed.

Secondly, since it is designed with colder heat ranges, this product is capable of handling intense conditions. Perhaps that’s the reason why it’s used by professional car drivers who regularly test the limits of their engine to beat the competition.

To complement its cold heat range, the Yttrium-enhanced alloy reduces this plug’s side wire temperature by up to eight percent. That might not sound much, but the reduced temperature does play a part in improving this model’s shelf-life and decrease the chances of any pre-ignition.

4. Champion RC12YC Spark Plug

Despite being built to meet SAE and ISO standards, the Champion RC12YC has a price tag that won’t blow a hole in your pocket. The primary function of its TinTac seal is to prevent corrosion, which, in turn, results in secondary benefits like improved operating life of the spark plug.

Its patented semi-conductor resistor does brilliantly by suppressing both EMI and RFI. Both these electrical noises need to be dumbed down, or else they might interfere with the engine’s components. Hence why this spark plug is handy for both vehicles and OEM applications.

Regardless of what the engine load is, the heat-active alloy of this spark plug will allow the electrodes to achieve their optimal temperature. More importantly, the alloy will make sure that both the center and the ground electrodes retain that temperature, thereby ensuring their performance remains stable.

5. Denso (3297) SK20R11 Iridium Spark Plug

When was the last time you came across an iridium spark plug that wasn’t expensive than its competitors? Unfortunately for your budget, the Denso 3297 isn’t any different. Fortunately for your car’s engine, though, it has all the features to justify its (relatively) steep asking price.

Take the melting point of iridium to understand this point. Higher than that of most other metals, it enables this spark plug to withstand higher temperatures. Its platinum tipped ground electrode, on the other hand, increases the operating life of this unit.

What is more, even when this spark plug is sitting idle, it stabilizes combustion. You can also trust it to offer excellent performance and acceleration. So your vehicle won’t be the last to leave the line after the signal has turned green. Its price, though high, is meager when compared with other Iridium plugs.

6. ACCEL 8199 U-Groove Spark Plug

What is it that separates the ACCEL 8119 U-Groove from other spark plugs in this review? For starters, it will be delivered to your doorstep in a pack of eight. As long as you don’t run a V6 (which runs on 12 spark plugs), this unit’s package has got your entire engine covered.

Its quantity isn’t the primary reason behind this unit’s inclusion in this review. That credit has to go to its instant throttle response which also ensures fuel economy. You can also praise its extra-long shape which doesn’t allow flame/spark to dissipate and therefore prevents misfiring.

Need more reasons to take this spark plug seriously? Its central copper core has enormous thermal conductivity to ensure that your engine gets up and running at the first hint of ignition. Also, since its 14mm threads are machine rolled, they won’t do anything to harm your heads.

What is a Spark Plug?

Spark plugs are devices that transmit electrical current from an ignition system to the combustion chamber of an engine. They are only found in spark-ignition engines – those in which the air/fuel mixture requires a spark to be converted into energy.

Apart from helping in bringing the engines to life, spark plugs have other applications. They are used to measure ionization in the cylinders and ignite air/fuel mixture in furnaces.

Spark Plug Buying Guide

In contrast to the idea most drivers subscribe to, not every spark plug on the market is made for your car. Various circumstances make some units better (and others ill-suited) for your engine. They include the existing condition of your engine and driving conditions.

That means that you shouldn’t rely on the shopkeeper’s recommendation when choosing the right spark plug for your vehicle. Instead, what you should do is ask the following questions. Only then can you be sure that the unit you’re looking at can fulfil your requirements.

3 Key Considerations When Buying Spark Plug

Following are the questions you need to ask yourself before selecting a spark plug:

1. Type of Spark Plug / Material Spark Plug Is Made Of

   As you might already know, spark plugs do not come in the one-size-fits-all-engines category. Depending on the make of your engine and your car’s model, different types of spark plugs are available on the market. Let’s take a look at the most common ones among them:

   • Copper/Nickel Spark Plugs

     Apart from their inner core which is made of copper, these spark plugs boast nickel construction. The reason why they use copper on the inside is that it can conduct electricity with minimum resistance. Hence why most spark plugs you see on this review have copper cores.

     In terms of their benefits, these spark plugs work well in low-energy ignition systems. They are incredibly inexpensive and run brilliantly on natural gas engines as well. That’s why they are best for pre-80s vehicles or those that run on low voltage distributor-based systems.

     However, when compared with their counterparts, copper/nickel units have a smaller lifespan. That is especially true if you ended up using them in coil-on-plug (COP) or distributor-less-ignition (DIS) systems.

     Pros:
     – Inexpensive
     – Run brilliantly on natural gas engine

     Cons:
     – Smaller lifespan

   • Platinum Spark Plugs

     In contrast to their copper counterparts, platinum spark plugs are available in two types: single platinum and double platinum. While the former uses platinum only in the construction of its electrode, both the cap and the electrode of the latter are made of platinum.

     That’s why both these spark plugs come handy in different types of vehicles. Single-platinum models are made for those with an electronic distributor ignition system. The double-platinum spark plugs, meanwhile, are recommended for cars with a waste spark system.

     Regardless of their type, platinum spark plugs work brilliantly in low temperatures. You can also count on them to be more efficient than copper. The fuel-efficiency they provide also dwarves that of copper/nickel plugs. However, they are more prone to overheating.

     Pros:
     – Work well in low temperatures
     – Better fuel efficiency

     Cons:
     – Prone to overheating

   • Iridium Spark Plugs

     When compared with copper and platinum spark plugs, those that are made of iridium perform better on multiple counts. These units can last longer (between 50,000 and 60,000 miles) and can provide the necessary spark to bring your engine to life at much lower temperatures.

     Yet another way they justify their steep asking price is by bringing down your vehicle’s fuel consumption. They have a tiny electrode in the middle which reduces the voltage these spark plugs would need to bring your engine to life. That, in turn, means you can enjoy savings on fuel.

     Most new vehicles that you see on the road have iridium spark plugs. Provided yours has them as well, do not replace them with platinum or copper. Or else, you might end up decreasing the performance of your vehicle just to save a few extra dollars.

     Pros:
     – Long lifespanGreat durability
     – Require less voltage

     Cons:
     – Pricey

   • Silver Spark Plugs

     These units have their tips made of silver and offer excellent thermal conductivity. They are specially made for engines whose combustion chamber temperature is higher than that of newer vehicles. You can find silver spark plugs in motorcycles as well as some older European-made performance cars.

     The main reason why they are no longer used by vehicle manufacturers is their short-operating life. Since they work at higher temperatures, the wear these spark plugs incur is excessive. That’s why we do not recommend silver spark plugs to our readers.

     Pros:
     – Excellent thermal conductivity

     Cons:
     – Short operating life

2. Heat Rating

   The heat rating of a spark plug tells you about the temperature range in which the plug will work optimally. It is indicated by a number, with higher numbers indicating that the spark plug would do well in colder temperatures.

   • Low Heat Rating

     Spark plugs with a low heat rating (generally between 2 and 5) are made for light-duty vehicles. Their firing end heats up quickly, and they expose a bigger surface area to hot gases.

   • High Heat Rating

     Also known as cold-type plugs, those with a high heat rating don’t let their firing end heat up too quickly. It is this property that makes these units a must-have for performance vehicles.

3. Electrode Gap

   Measured in millimeters as well as inches, the electrode gap of a spark plug is crucial for proper engine performance. That’s because it’s the gap that determines the magnitude of the spark and, by extension, the combustibility of the air-fuel mixture.

   • Narrow Gap

     Plugs with a small electrode gap fire on almost every cycle. However, since they give too little space to the air-fuel mixture, such plugs are more prone to getting dirty from incomplete combustion by-products.

   • Wide Gap

     Plugs with a wide electrode gap won’t fire on each cycle, but you can count on them to give a clean burn. Also, they have the unfortunate tendency to misfire at high speeds.

Crucial Tip: Make sure that the gap of your spark plug is the same as mentioned in your vehicle’s instructions manual.

4 Important Spark Plug Features and Specifications

Following are the features and specs which are a must-have for the top-rated spark plugs:

1. Compatible:

   Make sure that the spark plug is compatible with your vehicle’s engine, its transmission (manual or automatic), the engine’s displacement (space when the engine is at its lowest piston point), and its electrode gap.

2. Long-Lasting:

   Regardless of the material of construction of your spark plug, it must last north of 40,000 miles. The best models can last as much as 70,000 miles, though they come with an eye-watering price tag.

3. Easy to Install:

   Almost all the spark plugs you see in this review have one thing in common: they’re a cinch to install. Without requiring any tools, users without any prior experience can install (or remove) them with bare hands.

4. Corrosion-Resistant:

   Since they have to deal with lots of wear and tear, only those plugs that can keep rust at bay can outlast their warranty period. Corrosion-resistant plugs also save you from problems like rough idling and misfiring.

Differences Between a Cold and Hot Spark Plug

As you might already know, the main reason for being of spark plugs is to transmit a bolt of electricity across a gap. The gap is nothing but vacuum, and for the electricity to get across it and produce a powerful spark, it has to be at a very high voltage, which lies somewhere between 40,000 and 100,000V.

Apart from ensuring the transmission of the spark, the spark plug, which is in contact with the engine, has to withstand the engine’s heat at all times as well. If that wasn’t a tough task on its own, spark plugs also have to prevent the build-up of additives on their upper surface.

To perform these three functions (transmit the spark, withstand engine’s heat and keep wear and tear at bay), every spark plug has a ceramic insert. It is the functioning of this ceramic insert that classifies spark plugs between hot and cold units.

• Hot Spark Plugs

  These are units whose ceramic insert’s tip gets hot when it comes into contact with the metal part of a plug. Their temperature sees an increase because their surface area (which comes into contact with the metal part of a plug) isn’t as big as that of a cold plug.

  For this reason, when heat goes through that small surface area, it doesn’t find much space to dissipate. That forces the heat to accumulate itself on the tip. For this reason, hot spark plugs burn off more deposits (less corrosion) and achieve less transfer of heat.

  • Pros:
    Prevent corrosion better
    Best for normal vehicles
  • Cons:
    Achieve less heat transfer

• Cold Spark Plugs

  As you might have guessed by going through the previous two paragraphs, cold spark plug’s ceramic insert doesn’t get hot. That, in turn, happens because of the larger surface area of the tip. Just like the best brake pad, the tip allows heat to dissipate quickly into the surroundings.

  This mechanism has both plus- and negative points. On the plus side, colder plugs are recommended for performance cars that require a bigger boost to get their engine up and running. On the flip side, cold spark plugs are less-resistant to the build-up of corrosion.

  • Pros:
    Achieve better heat transfer
    Best for performance/sporty vehicles
  • Cons:
    Might not be able to keep corrosion at bay

What Does a Spark Plug Do?

Engines are pretty extraordinary machines. They take the gasoline you put into your car’s fuel tank and convert it into energy. The process isn’t as simple as it sounds, as a lot of moving and non-moving parts are involved in this conversion of fuel into energy.

One of those parts is a spark plug. To understand its importance, it’s crucial that you first know the working of an engine. Only then you’d be able to realize why vehicles with faulty spark plugs suffer from problems like rough idling or misfiring.

To spare you the technicalities, we’re going to discuss the engine’s working in layman terms. The first step in the engine cycle (the working of the engine) is the intake of air and fuel. As both these substances enter into the engine’s piston via one of the latter’s valves, the piston starts moving upward.

The reason why the piston moves upward is to compress the air/fuel mixture. It keeps on compressing the mixture until, at one point, the pressure is so high that the mixture requires a minor spark to light up. The responsibility of providing that spark is on the spark plug.

How Spark Plugs Work?

To understand how spark plugs work, it’s crucial to know about the parts which play a role in its working (i.e., in transmitting the electrical current). Those parts include:

• Insulated center electrode
• Heavily insulated wire
• Ignition coil
• Grounded terminal on the plug’s base

Once you turn the key in the ignition, high voltage is generated in the ignition coil. The heavily insulated wire, which connects the coil to the insulated center electrode of the plug, transmits that voltage to the spark plug. This creates a voltage difference between the center electrode and the grounded terminal located on the base of the spark plug.

Initially, due to the insulation provided by the air/fuel mixture inside the engine’s piston (to which the spark plug is connected), the spark plug won’t fire. That ‘gap’ is ultimately breached when the voltage coming from the coil exceeds the 20,000 volts mark.

Once that gap is breached, the spark plug produces intense heat which creates the spark necessary to light-up the air/fuel mixture inside the piston. This process converts the air/fuel mixture into heat energy and brings your car’s engine to life.

4 Important Benefits of Replacing Your Spark Plug

Following are the benefits of replacing a spark plug:

1. Achieve Complete Combustion
   Spark plugs that ensure complete combustion of the air/fuel mixture inside the piston of your cylinder provide two benefits. First, they ensure that problems like rough idling or misfiring are history.
   Second, complete combustion of fuel results in less pollution, as fewer by-products are produced, and later on, emitted into the atmosphere. That means that new spark plugs help decrease your carbon footprint.
2. Better Fuel Economy
   Don’t care much about the environment? Then there’s another reason which might be closer to your heart (and pocket) as to why you should replace your spark plugs more often.
   That reason is given by the National Institute for Automotive Service Excellence, which states that poorly-maintained spark plugs can reduce your car’s fuel efficiency by 30%.
3. Smooth and Seamless Starts
   Is there anything better than having a car that starts on the first ignition? People whose cars take ages to wake up their engine from deep slumber can attest that there’s nothing more infuriating than jerky starts.
   These rough starts mostly happen either due to the build-up of corrosion on the spark plug. Or they occur because the spark plug has deteriorated from wear and tear. Only replacing the burnt-out model will resolve this problem.
4. Less Harmful Emissions
   According to the US Environmental Protection Agency, regular engine check-ups – especially those that tune-up the spark plugs – can help humans get a grip on air pollution.

Why Spark Plugs Needs Replacement

Even if they haven’t outlasted their warranty period, there are a lot of things that could happen to your spark plugs and necessitate replacement. Some of them include:

1. Build-up of deposits
   The air coming out of the engine passes over the exposed tip of the spark plug at full speed. The oil that enters the engine might also contain contaminants which it may deposit on the plug’s surface.
   All these contaminants may contribute toward the pre-ignition of your car (a phenomenon that contributes to engine deficiencies) by building deposits on the plug’s surface.
2. Wear and Tear
   Apart from the elements mentioned above, spark plugs come into direct contact with lots of elements. Some of these elements, like dirt or dust, cause wear and tear on their surface.
   After some time, this wear and tear might decrease the effectiveness of spark plugs and, by extension, that of your engine.
3. Overheating
   Provided your engine’s cooling system isn’t working properly, it will heat-up your engine. Spark plugs, which are connected to the engine, won’t remain shielded from the build-up of heat in such a scenario.
   That means that when you replace your spark plugs, you’ll be bidding farewell to all those days in which your vehicle came to life in a jerky, erratic manner.

When & How To Change Spark Plugs

Following are the things you need to know about the replacement of your spark plugs:

How to Remove & Replace a Spark Plug in 5 Steps

Here are the steps you need to follow to remove and replace your spark plug:

• Step 1: Turn off the engine

  Don’t touch the engine if you’ve just parked your car in the garage. That’s because the entire engine, its exhaust system as well as the plugs, will be too-hot-to-touch. Only after you have turned off the engine and let it cool down for at least 15 minutes should you go anywhere near it.

• Step 2: Gather the tools

  To remove and replace spark plugs, you’d need the following tools:

  • A ratchet socket drive wrench
  • An extension bar
  • Spark plug socket
  • A feeler gauge or spark gap gauge

• Step 3: Locate spark plugs

  On opening the hood/bonnet of your car, you usually see wires heading under the engine. More often than not, spark plugs are on the engine-side of these wires. They are mostly hidden under the plug covers that shield them from external elements.
  For instance:

  • If you have a 4-cylinder engine: Spark plugs will be on top of the engine, in the front row.
  • If you have a V8: Spark plugs will be on the left and right side of the engine

• Step 4: Remove spark plugs

  Grip the base of the spark plug using a socket wrench and remove it slowly from its housing. Don’t try to yank the plug out of the housing, or else you might have a ruined spark plug to deal with. You should fit the square end of the wrench into the spark plug socket’s square hole.

  Afterward, turn the wrench counterclockwise to loosen the spark plug. You might get more leverage by placing your free hand over the wrench’s head to grasp it firmly. Once the wrench starts turning freely, finish the job by removing the wrench and manually turning the socket by hand.
  Keep on going until the plug is detached from the engine.

• Final Step: Replace the plug

  Once you’ve removed the plug and used the instructions given in the car’s manual to purchase a new one, use a wire brush to clean the plug’s port as well as the wires leading to it. You aren’t going to clean them often, so make sure to clean them properly.

  Then remove the plug covers and put the new spark plug in place. At first, tighten the plug by hand and follow it up by tightening it using a wrench. Don’t over-tighten it as that might strip the threads and ‘free’ the plug.

When to Change Spark Plugs

Following are the telltale signs that you might need to change your spark plugs:

1. Engine is Rough Idling

   Is your car giving off strange vibrations without any rhyme or reason? Hearing harsh and jittery sounds coming out of its engine? If that’s the case, then it means your engine is rough idling.
   All engines idle when the car is parked. However, if the spark plugs aren’t clean and not as effective as they should be, the idling becomes rough. Not resolving this problem can lead to engine damage.

2. Car isn’t Starting Smoothly

   In contrast to the idea most drivers subscribe to, its battery isn’t always the culprit when your vehicle isn’t starting. One possibility most of us ignore is worn-out spark plugs.
   After all, these tiny-looking units are responsible for providing the spark that would ignite the air/fuel mixture and bring your engine to life. If the flash isn’t there, your car will take multiple (or extended) ignitions to start.

3. Engine is Misfiring

   A misfiring engine will make everyone sitting inside the car aware of its predicament by sending jitters and vibrations. Damaged spark plug wires or worn-out spark plugs might cause the engine to misfire.
   Provided you choose to ignore the signs, your car might face several effects. They include a reduction in its performance and a decrease in its efficiency.

4. Engine is Surging

   Worn-out spark plugs might force your engine to take in more air than necessary. This disturbs the composition of the air/fuel mixture inside the piston, leading to incomplete combustion.
   Once that happens, your car will start to stutter. This continual starting and stopping of the car is a dangerous phenomenon, especially if you’re driving it at high speeds.
   If it doesn’t stop, we recommend we can help you in choosing a car ramp. It would let you park your vehicle on an incline and carry out a thorough inspection of the engine.

5. Car is Consuming More Fuel

   Are your trips to the gasoline station becoming more frequent even though there’s no change in your daily driving routine? Spark plugs might be the reason why your car’s fuel consumption has suddenly gone up.
   Experts tell us that worn-out spark plugs might decrease a car’s efficiency by as much as 30%. So you might want to change your car’s spark plug to return its fuel consumption back to the optimum level.

6. Poor Acceleration of the Car

   Has the ‘pick’ of your vehicle gone down? Other cars leaving you behind once the signal turns green? This sluggish behavior of your vehicle can also be attributed to a worn-out spark plug.

And if you’re planning to change your oil, our floor jack reviews will give your ride the lift it needs!

FAQs and Answers

• Q: What happens if you use the wrong spark plugs?
  A: Flattened or broken electrodes are indicators that you’ve installed the wrong spark plug. Provided the spark plug is too long, it might end up causing damage to the engine. A shorter-than-recommended unit, meanwhile, might lead to spark plug fouling and poor gasoline mileage.
  Always check your car’s owner’s instruction manual to ensure that you’ve purchased the correct spark plug for your vehicle.
• Q: How often should you replace your spark plugs?
  A: Those spark plugs that come pre-installed in your vehicle mostly have an operating life of 100,000 miles. However, the replacement units that you purchase from the market, especially iridium and double-platinum, might last longer.
• Q: What happens if your spark plugs are gapped wrong?
  A: Incorrectly gapped spark plugs make you aware of your mistake by showcasing the following symptoms:
  – Rough engine idling
  – Engine hesitation
  – Poor engine performance
  – Engine knocking
  – Engine missing

Conclusion

One of the best compliments that we could play to spark plugs is that they are mood saviors. Whether you’re going to attend a friend’s wedding, in the process of dropping your little one at school, or are running late from office, your mood will most likely get ruined if the car won’t start.

The best spark plug look after your pocket as well. That they do by enhancing your engine’s performance and reducing your vehicle’s fuel consumption. So you can trust them to make your trips to the local gas station as few as possible.

What’s more, as we have stated in our spark plug reviews, they also protect the environment. After all, by preventing premature ignition and ensuring complete combustion of the air/fuel mixture inside your engine, they make sure that the air you breathe remains free from harmful gases.