Best Spark Plugs to Buy In 2021? (Reviews and Buyer’s Guide)

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Using the best spark plugs is a key aspect of having a proper engine performance without misfires.

Of course there's plenty more involved but today we're going to focus on the spark plugs. 

During the last 10 years I've changed quite a few plugs and diagnosed plenty of problems related with spark plugs and there's been a few brands and sparkplug series that have worked brilliantly for me.

Here are my favorite 5 sparkplugs reviewed and then there's a comprehensive buyer's guide to help you understand this piece of engineering better and making the right choice.

Comparison Chart

1. NGK Laser Platinum Spark Plug
  • High ignitability and long life
  • Slow wear rate for a stable idle, reduced emissions, fuel efficiency and top-notch antifouling
  • Dual ground electrodes provide a consistent and reliable spark
2. Autolite Iridium XP Spark Plug
  • Autolite’s superior design features, including finewire design and platinum sidewire technology improve ignition and help drivers experience optimal auto performance
  • Guaranteed for seven years
  • OE-equivalent design adapts for every engine to ensure the proper fit
3. Denso Platinum TT Spark Plug
  • Very popular and affordable
  • Twin tip technology gives drivers exceptional performance and increased ignitability
  • Designed to withstand extreme stress for a longer functional life
4. Denso Iridium Power Spark Plug
  • Super narrow central electrode improves firing time and engine performance
  • Quality construction ensures plug longevity
  • U-Groove technology allows ground electrode to achieve increased ignitability an minimizes voltage required
5. NGK Iridium IX Spark Plug
  • Trivalent Metal Plating resists corrosion and seizing
  • Long insulator nose provides anti-fouling and corrugated ribs halt flashover
  • May reduce misfires

Spark Plugs Reviews

1. NGK Laser Platinum Spark Plug

This platinum electrode plug is laser welded to target quick starts and quick acceleration.

It features a 1.0mm platinum electrode and a pre-calibrated .031" (0.8mm) gap size.

The NKG  spark plug is a superior anti-fouling plug that delivers consistent performance with each fire.




2. Autolite Iridium XP Spark Plug

The Autolite Iridium XP spark plug highlights a 0.6mm finewire iridium-enhanced center electrode for quick response and superior ignitability.

This plug is designed to withstand the rigors of performance driving and each plug is precisely set for the perfect gap and performance

It comes with an incorporated motor seat gasket and terminal nut for easy installation.




3. Denso Platinum TT Spark Plug

This plug is designed to withstand the rigors of performance driving and each plug is precisely set for the perfect gap and performance




4. Denso Iridium Power Spark Plug

The Denso IK20 Iridium Power spark plug boasts the smallest central electrode on the market: a 0.4 mm iridium power core.

This plug delivers incredible firing potential for faster flame growth and reduced heat loss.

Manufactured with DENSO’s custom 360-degree laser welding process, this spark plug features a quality bond and unbeatable structural integrity.




5. NGK Iridium IX Spark Plug

This plug features a fine 0.6mm laser welded Iridium tip for consistent spark and high durability.

It is designed for the performance car and can deliver superior ignitability and improved throttle reaction.

The Iridium-alloy can withstand heat and electrical wear for an extended plug life.




 Spark Plugs Buyer's Guide

How do I know which spark plug to buy?

Easy option: Check owner's manual and just buy those ones. They will surely fit and do the job although they won't necessarily be the best.

Best option: Check Autozone's compatibility tool , introduce your car's year, make model and engine and it will give you a few options from different brands. Note the code and check if any of those spark plugs is the ones I recommend. You can then click on the pic here to check prices and availability on

Electrode Materials

Choosing the correct spark plug for your performance vehicle is essential for getting the most out of your engine. One of the main factors that determines your spark plug function is the electrode material that you choose. There are three primary electrode materials:

  • Copper - Copper is the most widely used electrode material for spark plug design. Copper plugs are very popular for use in performance and modified vehicles because they conduct more efficiently than do iridium and platinum. They have the shortest lifespan of the three conductor materials and generally need to be replaced every 20,000 miles.
  • Iridium - Iridium alloy electrodes feature a high melting point and are very durable, so they last twice as long as copper plugs do. The conductivity of the iridium plug is lower than that of copper and the price point is higher however, the properly calibrated iridium plug can be an ideal option for the performance vehicle.
  • Platinum - Platinum is also a higher quality electrode material, like iridium, and is often preferred for newer cars. Platinum spark plugs are usually not recommended for performance engines, as they have slower conductivity.

Once you have chosen the electrode that works best for your engine mod, you can consider the other factors that influence plug performance: heat and gap setting. You will need to choose the proper settings for your heat and gap setting in order to get your engine to perform at peak levels.

Temperature Grades

Determining your engine’s specific heat range requires referencing your car’s manual and a bit of guess work.

Your fuel will burn within a specific range, and you need to take care to pick spark plugs that do not burn too hot for your engine’s range.

Though hotter plugs will generally lead to faster sparking, going too hot is a danger to your engine and may cause other problems further on down the road.

You also want to take care not to pick a plug too cool for your engine, as it may run too cooly to properly self-clean and will retain unwanted buildup.

Spark plug heat ranges are determined by the length of an individual plug’s insulator tip. The longer the insulator tip, the hotter the plug will run; the shorter, the cooler.

Hot plugs pull heat from the combustion rather slowly and quickly achieve temperature higher than the deposition zone.

Cold spark plugs quickly remove heat from combustion and prohibit advanced ignitions as a result.

Spark plugs manufacturers use thermal values to communicate insulator tip information to consumers.

Typically higher the thermal value, the longer the tip, while lower thermal values signify shorter tips; thus, hot plugs will have a higher thermal value than low ones. Often these numbers are communicated in the part numbers for the plugs and may stand alone or be the last number(s) at the end of an ID string.

Spark Plug Components

The construction of a spark plug goes a long way to determining its overall performance. And while there is great variation among the spark plugs on the market, each plug has the same basic structure, including the following components:

  • Terminal - The terminal is at the top of the spark plug and connects to the ignition system. Terminal constructions varies depending on use, but typically features spark plug wires or eyelet connectors for integration into the system as a whole.
  • Insulator - The insulator is made of a thick hardened ceramic, which is glazed to provide improved resistance for surface spark tracking. It gives support and protection to the central electrode and conducts heat to reduce extended lighting and glowing.
  • Ribs - The ribs are a deeply grooved portion of the spark plug that works to lengthen the distance between the terminal end and grounded end of the plug. The design works to encourage increased electrical insulation and provides protection from energy leakage.
  • Insulator tip - The insulator tip is essential for thermal conduction and is made from hard ceramic. It is designed to withstand heats of up to 650 degrees Celsius.
  • Seals - Spark plug seals stop leakage from the combustion chamber.
  • Metal shell - A spark plug’s metal shell withstands torque associated with tightening the plug and works to draw heat from the insulator and move it through the central electrode to the ground electrode.
  • Central electrode - The central electrode is the hottest part of the spark plug and directs heat from combustion away from the tip with a burst of electrons, thus creating the spark that the engine requires for function. The central electrode also self-cleans the spark plug with intense heat to keep it running smoothly.
  • Ground electrode - Made from nickel steel, the ground electrode is on the side of the metal shell and works to neutralize charges leaving the spark plug to protect the other parts of the engine.


During installation, the spark plug is calibrated to a very specific gap distance for jumping the spark. This distance is determined by individual engine requirements and is somewhere in the range of 0.6-1.8 mm.

The gap must be calibrated precisely in order to deliver proper sparking to your engine.

Too narrow of a gap will lead to an insufficient spark, reducing the engine’s power and efficiency.

Too wide of a gap may lead to misfires, especially at high revs.

Final Verdict

Choosing the best spark plugs for your vehicle can help you to experience better engine performance during every drive.

Armed with knowledge about which spark plugs may work best for your application and information from your own car’s manual, you can find the best solution for the performance that you’re looking for.

Last Updated on 10/01/2021

3 thoughts on “Best Spark Plugs to Buy In 2021? (Reviews and Buyer’s Guide)”

  1. Hi. Want to do service on my vehicle (2004 Acura TSX). Please advice me which are the best best spark plugs to use. The best of the best, cz am confused.
    Also for the oil, which is the best oil change to use for a high mileage car. I got 211000 miles. I bought it with 208K now i want to give it the best. Also advice on the oil filter.
    Thanks in advance.

    • Hey Solomon, here are my recommendations.

      For the spark plugs I’d go with OEM’s NGK Iridium (part nº NGK 6994)

      For the oil, I always lean towards synthetic oil, and in your case on a high mileage car, you want to go with real high quality oil. The first gen TSX runs on 5w30 and for that SAE i recoomend going for Pennzoil Ultra Platinum ( Royal purple’s got a few too many additives that may not do well for a high mileage engine. Another good choice is Valvoline MaxLife. In any case, just make sure to go with 5w30. Newer versions of the TSX use 5w20 and some people get confused.

      Then for the oil filter, Mobil 1 is my go-to choice. For your 2.4L engine, you need part M1-110 (you can read more on this filter here). Bosch FILTEC are another great choice. The model that fits your car is the Bosch 3323. I’d personally go with Mobil 1 but any of the two will do a great job.

      I hope this helps and let me know if you have further questions

  2. Great advice Alex I concur 100 %. I try to stay with Royal Purple in my Accord 2.4 SULEV. But Mobile 1 and Pennzoil Platinum are very good synthetics as well! I stay with Mobil 1 filters! My 2.4 also takes the M1-110! The oil is the life blood of the vehicle!!!! Take care of your engine it will take care of you! Jeff Verry UPState NY..

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