Engine Servicing

The Best Spark Plugs In 2020 (With Buying Guide And Reviews)

best spark plugs

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Best spark plugs | Editors' Choice

Amazon.com prices as of  2020-08-10 at 08:27 UTC Details

If your engine is not performing as it should, checking the condition of its spark plugs is a good place to start your diagnostic procedure. There are a few different types of spark plugs, and it's essential that you fit the right type and replace them at the proper service interval. 

In my opinion, one of the best spark plugs at the moment is the DENSO 4504 PK20TT Platinum TT, check out the full review below

Checking and replacing your car's spark plugs is a cheap and easy job. There are many different brands of plugs on the market today, all claiming to be better than the rest, so it can be difficult to find the best spark plugs for your vehicle. 

It's important to check your vehicle manufacturer’s recommendations before messing with the spark plugs. Using the wrong type of spark plug can be catastrophic for your car's engine. 

How Do Spark Plugs Work?

All spark plugs work in basically the same way.

In a standard four cylinder, four stroke engine, each spark plug will fire and causes a small explosion of the compressed air and fuel mixture in the chamber. This forces the piston outwards which delivers the power to turn the crankshaft.


Above is a simple overview of how a spark plug operates in an engine 

At say, 800 rpm, each spark plug will fire around 400 times per minute. As the engine speed increases, so too does the rate of firing.

This is why it's important to choose a reliable spark plug. To run reliably and efficiently, the engine needs spark plugs that are capable of withstanding high pressures and high temperatures over many miles.

Bad spark plugs can lead to all sorts of problems with engine performance and the fuel injection system. It can also make starting your car a whole lot more difficult than it has to be.

How Often Should You Change Spark Plugs?

Over time, the condition of your cars spark plugs will deteriorate. So how do you know when it's time to change the spark plugs?

Under normal conditions, spark plugs can last around 100,000 miles between changes. But sometimes your car will show signs that you need to change your spark plugs sooner. This can be down to how you drive your car, or simply be down to the quality of the spark plug. 

In general, bad spark plugs will usually cause problems with engine performance and fuel economy. Here are a few tell-tale signs of failing spark plugs.

Symptoms of Bad Spark Plugs

  1. Engine Misfire - If a spark plug isn't providing the right spark at the right time, then it will cause the engine to misfire.
  2. Car revving or hesitatingThis is a side effect of an engine that isn't running properly, or is misfiring. It can also be caused by other engine parts such as faulty sensors, injectors, a slipping clutch or a bad fuel filterIt's worth ruling out the spark plugs too as a possible problem.
  3. Trouble starting the engine - Dirty or worn spark plugs won't deliver a clean spark needed to fire up the engine. An engine that won't start can also be caused by a problem with the battery or charging system.
  4. Bad fuel economyA spark plug that isn't performing well, will cause an over-compensation in the fuel air mix by the ECU. This will cause the engine to run rich and use more fuel.
  5. Rough engine idleA badly running engine will usually be more noticeable when idling. A bad engine idle is often caused by bad spark plugs, among other things.

If a bad or failing spark plug is suspected, then the next step is to remove each plug and visually inspect them. Here are a few signs of a bad spark plug.

  1. Wet or oily deposits - Oil on spark plugs can be caused by a leaking head gasket (engine coolant is getting into the combustion chamber). It can also be caused by leaking piston rings or an overly rich air/fuel mix. In direct injection engines, the amount of fuel fed into the engine is controlled by the ECU. Sometimes a bad or failing fuel injector will mess up the air fuel mix. 
  2. Glazed/Glossy Electrode Tip - This indicates a spark plug that is regularly over-heated. This can be caused by an overly lean air fuel mix. It can also be caused by a spark plug that is loose in the engine.
  3. Dark colour - If the spark plug is covered in dark wet or dry deposits, then this is an indication of an engine that is running rich (too much fuel). This can also be caused by a vacuum leak or low cylinder compression. In older cars, it can point to an issue with the engine timing or too large of a plug gap. In newer fuel injected cars, the timing is controlled by the ECU. 
symptoms of bad spark plug

Two old spark plugs

ridium spark plugs, 

These are the most durable and long lasting plugs on the market. 2

What are the benefits of changing spark plugs regularly?

  • Easier engine starts. Jerky starts and misfires can be caused by a dirty buildup and worn plugs. New and upgraded plugs can fix this and transform your car on startup especially under adverse conditions
  • Improved acceleration - A common sign of worn spark plugs is sluggish performance. Replace those plugs for better sparks and better performance
  • Improved fuel efficiency - save money by reducing fuel wastage and improving engine combustion efficiency, often by up to 25%
  • Reduce harmful emissions - if you car is running as efficiently as possible, it will be kinder to the environment and run as well as it did when it left the factory

What are the Different Types of Spark Plugs?

Basically, the spark plugs we are talking about here today all fall into one of four broad categories. 

There is a lot of mis-information out there when it comes to spark plugs. Which is better, platinum or double platinum plugs? Do iridium plugs last longer? Aren't all spark plugs made from copper?

 So let's set the record straight once and for all.

Keep in mind though, even after establishing which type of spark plug that you need, there will be still be slight differences, depending on manufacturer specifications. So it’s important to double check which specific type your manufacturer recommends.

1. Copper Tipped Spark Plugs

These are the original type of spark plug and today are only really used in old (pre-90s) cars and some high performance/modified cars. Basically these plugs are made of a copper core, with a large nickel alloy electrode.

Copper offers the best conduction, hence the reason they are still used today in modified, high performance engines.  

But on the flip side, they are not the hardest wearing plug. Using copper spark plugs will shorten your engine’s service interval considerably as they wear out a lot quicker than platinum or iridium plugs. Copper plugs generally only last up to 30,000 miles and can be badly worn after only 6 months. 

So even though t hey are a favorite of budget-conscious car owners thanks to their low cost, they don’t last half as long as other spark plugs, and are not suited to most unmodified modern cars, especially those that operate under adverse conditions and do high mileage.

2. Single Platinum Spark Plugs

These are quite similar to their copper-tipped counterparts, except they can last as long as 100,000 miles.

Featuring a much harder wearing platinum tipped electrode, they usually operate at a higher temperature to their copper counterparts. This reduces carbon build up and keeps them looking newer and performing better longer  .

A popular choice in newer vehicles, they will last much longer than copper plugs and are chosen by manufacturers' to extend service intervals. 

3. Double platinum spark plugs

These are a little bit more expensive than single platinum models, but they offer a higher performance and a longer life. As the name suggests, they feature platinum discs on the centre electrode and on the outer electrode.

Originally designed to take advantage of waste-spark DIS systems, this type of plug features two platinum discs, one on the centre electrode and one on the outer, side electrode.

It's important to note that double platinum spark plugs are not simply twice as efficient as single platinum plugs. They are actually used in specific engines with a particular type of coil and firing process. Because of this, you should never downgrade to copper of single platinum plugs if your car has double platinum plugs installed from the factory.

4. Iridium spark plugs

These are the most durable and long lasting plugs on the market, typically lasting 25-30% longer than platinum plugs.

Just like  platinum plugs, the tip of the centre electrode is modified, this time with an Iridium alloy tip. To keep costs down and to improve conductivity, this tip is usually a tiny 0.4-0.6 mm in diameter.

Because the iridium alloy is hard wearing and not as good a conductor as platinum, it will last longer and generally run cooler.


An iridium spark plug (right) compared to a standard plug on the left

Again, don't downgrade from iridium plugs to copper or even platinum if your car is already running  with this type of plug. Many manufacturers today require you to use only Iridium plugs with their coil on plug systems, so downgrading could have an adverse reaction.

The Best Spark Plugs -  Detailed Reviews

Our Top Pick - 'Best Spark Plug'

Amazon.com prices as of  2020-08-10 at 08:27 UTC Details

Main Features
  • Twin Tip technology- featuring both platinum and titanium tips
  • Excellent corrosion resistance
  • Purified alumina powder insulator

Denso claim that they are the pioneers of  titanium spark plug manufacturing. I've personally used Denso plugs for years in all sorts of trucks and cars. If a Denso plug is available, it's usually my go to brand and performance wise, they haven't let me down yet.

By using platinum and titanium in the 4504, they've increased the natural corrosion resistance of the plug. Titanium is also a great conductor. This allows for a tiny electrode tip of only 1.1mm.  The advantage of such a tiny tip is a cleaner, larger spark that requires less energy to fire. It also causes a bigger flame that spreads faster in the combustion chamber, thus increasing fuel efficiency

Another great feature of this plug is the purified alumina powder insulator. This improves the thermal conductivity of the plug. Thermal conductivity is important to the overall resistance of the plug to high temperatures. This means the plug can last longer than others, something I have seen time and again.

These Platinum TT plugs are available for a huge range of cars, trucks and SUVs. In many cases you'll find that these plugs were fitted to your car in the factory. If you are going to change them yourself, you can save a pile of cash by looking up the correct part using the Denso Part Finderrather than buying from a main dealer.

  • Help to provide better acceleration, faster starts and less chance of misfire
  • Will last longer, and will continue to spark effectively as they age 
  • They contain platinum. This gives an enhanced resistance to wear
  • Excellent value - Very low price for the quality
  • They are not iridium plugs, so won't suit all cars, especially newer models
  • They may not last as long as iridium plugs
'Best Platinum Spark Plug'

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Main Features
  • Fine platinum electrode tip
  • Trivalent metal plating that reduces corrosion
  • Triple gasket seal to make sure they stay tight and don't leak

NGK are another very popular spark plug manufacturer. The G-power range of plugs from NGK are a very popular choice as an after market plug. I've used them many times over the years, especially in German cars such as BMW and Audi.

This particular NGK plug is a pure platinum plug, no iridium or titanium. The electrode tip is constructed from platinum measuring a tiny 0.6mm in diameter. This minute tip means that a smaller voltage is required to make a good spark. Because the voltage is lower, the tip doesn't get as hot so will generally last longer. 

The ceramic insulator is made from a strong silicate material. NGK say that this is ribbed to help prevent flashover. Most plugs have this ribbed design, so it's not unique to the NGK plugs. I'm also not convinced that it will reduce the chances of flashover occurring. Flashover is usually caused by a damaged plug cap not fitting the plug properly. Or sometimes water vapour can get under the cap causing sparks between the terminal and the metal part of the plug. 

Another feature of these plugs is the trivalent metal plating used. This NGK say, enhances the anti-seizing and anti-corrosion properties of the spark plug. It's worth noting that you shouldn't use anti-seize with these plugs, as the trivalent metal plating changes the torque values. If you over tighten you run the risk of snapping the plug at the threads.

Overall, NGK plugs have a proven record of being reliable and long lasting. They are factory fitted too by many manufacturers. I'd have no problem recommending the G-Power range as my favourite platinum plug. 

  • Platinum tip provides consistent spark and reduces voltage
  • Faster starts and improved acceleration
  • Improved fuel economy and lower emissions
  • Anti-corrosion and anti-seizing metal plating, so they won't get stuck in your engine
  • No iridium in these plugs, so might not be as resilient as iridium plugs
  • Flashover can still occur with these plugs
  • Not available for as many car models as other plugs 
'Best Spark Plugs For Performance'

Amazon.com prices as of  2020-08-10 at 08:27 UTC Details

Main Features
  •  0.6mm laser welded fine Iridium tip
  • Iridium alloy electrode tip
  • Trivalent metal plated threads

These plugs from NKG are supposedly for the enthusiast, and are sold as performance spark plugs. They promise improved throttle response and greater resistance to wear, and are well suited to high performance engines.

They have the same features as the standard NGK plug. Trivalent metal coating, triple gasket seals and corrugated ribs on the insulator to help prevent flashing. The difference between these and the standard plugs is the 0.6mm iridium tipped electrode. Iridium is a really good conductor of heat and electricity. This means you get an even better spark at a lower voltage than with platinum or copper plugs.

To be honest, I only ever spend the extra on iridium plugs if they are specifically recommended by the vehicle manufacturer. I've never seen that much difference when I upgraded to iridium from platinum plugs. There are too many other factors that need to be taken into account when assessing engine performance such as the condition of the filters, ECU settings, fuel quality and driving style.

However, these plugs get lots of great reviews on Amazon. Some people make claims of massive changes to the performance of their car. 

These plugs are a great option if your plugs need changing and and the manufacturer recommends iridium. Like all NGK plugs, they are very well made and you are almost guaranteed they will perform well. One thing to note, if you do buy these plugs, make sure the gap is set properly before fitting them.

  • Iridium has high melting point, making it suitable for high performance engines
  • Excellent anti-corrosion and anti-seizing properties
  • Triple seals for reduced risk of leakage 
  • Gap needs to be set before fitting
  • More expensive than other plugs reviewed here
 'Best Long Life Spark Plugs'

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Main Features
  • Iridium tipped centre electrode
  • 5 rib insulator design, to prevent flashover
  • Machine rolled threads, to help prevent seizing

Iridium plugs are the standard in new cars today. These long life plugs from Denso, are factory fitted to many cars. You'll find Denso plugs in many Nissans and Chryslers, and they usually last the 100,000 or so miles that they advertise.

So you can be sure that if you put these in your car or SUV they won't let you down. Just like the NKG iridium plugs, they share many features with the platinum Denso plugs such as a ribbed insulator. 

Denso claims that these will improve the performance of your car. I doubt they will give you any extra horsepower, but they'll probably give you an extra few MPG from a tank of gas. It all depends on the state of the plugs that you are taking out. If they are in a bad way, then you definitely will see some improvement.

Overall, if you are a fan of Denso then you can't go far wrong with these plugs. Just don't expect miracles!

  • Should last for over 100,000 miles
  • Copper-glass seal for gas tight installation
  • Copper core for heat removal
  • Iridium has high melting point, making it suitable for high performance engines
  • 5 Rib insulator 
  • Not suitable for all vehicles
  • You need to check the gap before fitting
'Best Dual Platinum Iridium Spark Plugs'

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Main Features
  • Four ground electrode design
  • Maintenance free
  • Fused iridium and platinum centre electrode

Bosch say that these spark plugs offer the latest in spark plug technology and design. The Fusion range of plugs have an iridium and platinum centre electrode. The combination of the two alloys makes the iridium stronger, less brittle and a better conductor of heat and electricity. 

These plugs have a four yttrium enhanced ground electrode. This is self-cleaning because of the crazy  high temperatures produced by the spark. This means that they are less likely to oxidize and therefore should last longer.

In the long run, these plugs may very well perform better and longer than any others on this list. To be honest, if you get 70,000+ miles out of any plugs, you should be happy with that. For most people that's a few years of driving.

The downside to these plugs is that you will need to lay out more cash upfront, so depending on your expectations and driving style they may not offer as good all round value. 

  • Self-cleaning electrode 
  • Four ground electrode design 
  • Fused Iridium and Platinum center electrode that produces a more powerful spark
  • No ribbed design on the insulator body. 
  • Unusual electrode design, may increase chances of failure
  • Not compatible with as wide a range of vehicles

What are the best spark plugs you can buy?

Well, the top place goes to the Denso Platinum TT range of plugs. In my opinion, they offer the best all round value for money. Add to that, Denso have been around for years and are pioneers in spark plug innovation and design. 

Just remember, if you are looking to upgrade the spark plugs in your car, choose  a platinum, titanium or iridium based plug for longevity and for the best performance.

All of the plugs in our list will offer excellent performance over a longer period of time so as long as they meet the requirements for your car then you can't go wrong.

The Best Spark Plugs


DENSO Twin-Tip Spark Plug


The DENSO Twin-Tip Spark Plug is a platinum spark plug that promises to produce sparks at a greater speed per second than its competitors, which ultimately makes for a more complete combustion and increases fuel economy tenfold. The center and ground electrodes are coated with platinum, which increases the plug’s durability and resistance to corrosion.

Features and Specs

  • 11 mm platinum center electrode and similarly sized reinforced titanium ground electrode
  • Purified alumina powder insulator for greater dielectric strength and resistance to stress
  • Weight of 0.3 ounces
  • Promotes fast start and complete combustion
  • Above average lifespan

NGK Standard Spark Plug


As the name suggests, the NGK Standard Spark Plug is straightforward and simplistic in its design, offering few, if any, of the “fancy” features seen on some other spark plugs. That being said, it does what it says it is going to do and it does it with startling effectiveness. With one of these spark plugs fitted inside your engine’s cylinder head, your engine will run for miles on end. 

Features and Specs

  • Specially designed for smaller engines
  • Weight of 2.1 ounces
  • Leaves factory pre-gapped
  • Easy installation
  • Resistant to corrosion caused by moisture and chemicals

BOSCH Platinum+4 Spark Plug


If you’re a car owner, I’m sure I don’t have to tell you that BOSCH is one of the most recognized names in the auto industry. Manufacturing pretty much everything you could ever require to keep your vehicle running smoothly, the brand is head and shoulders above its competitors. It is no surprise, then, that the BOSCH Platinum+4 Spark Plug has become so popular.

Features and Specs

  • Surface-air gap technology for improved fuel economy
  • Pre-set gap for easy installation
  • Weight of 1.9 ounces
  • Multiple yttrium-enhanced ground electrodes for longer spark
  • Above average lifespan

NGK Laser Platinum Spark Plug


This is the second spark plug from NGK to be featured on this list. Unlike the NGK Standard Spark Plug that we looked at earlier on, the NGK Laser Platinum Spark Plug features a unique design and many features intended to enhance its efficiency and prolong its life. Capable of enduring the immense pressure of supporting a larger engine, the NGK Laser Platinum Spark Plug is easy to install and a great choice for young drivers.

Features and Specs

  • Multi-ground electrodes
  • Easy installation
  • Pure alumina silicate ceramic insulator
  • Corrosion resistant
  • Weight of 1.9 ounces

DENSO Iridium Long Life Spark Plug


NGK isn’t the only brand with repeat appearances on this list. DENSO, the brand that kicked off our look at the best spark plugs, closes it with a well-deserved second entry. The DENSO Iridium Long Life Spark Plug is a great choice for drivers who don’t want to drop double figures on a platinum spark plug but don’t want the hassle of changing a copper-tipped model when it burns out.

Features and Specs

  • Harder and stronger than most platinum spark plugs
  • Weight of 8 ounces
  • Platinum-tipped ground electrode
  • Extra long lifespan
  • Iridium-tipped center electrode


Choosing the best spark plug for your engine is never going to be easy, but each of the plugs featured here will fulfill its purpose and then some. My personal favorite has long been the BOSCH Platinum+4 Spark Plug, which promises hundreds of thousands of miles of incredible power for virtually any engine in which it is placed. It may be a little more expensive than most other spark plugs, but if you have the money to spare you’d be crazy not to go for it.