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NGK spark plugs under the spotlight

Global automotive components supplier Niterra is an expert when it comes to NGK spark plugs. As a leading ignition and vehicle electronics specialist, the company has an almost 90-year history based on this key component that sits at the heart of every petrol-powered combustion engine.

No wonder then that in the EMEA region, the NGK Ignition Parts brand has over 1,900 part numbers available for spark plugs, which equates to coverage of around 80% of the 4-wheel vehicles in operation in this region. In Europe itself, there are 1,600 part numbers, covering more than 85% of 4-wheel vehicles. Parc coverage of 2-wheel vehicles is close to 100%. The importance of this component to Niterra is underlined by the staggering fact that by 1991, just 54 years after the company produced the first NGK spark plug, production had reached an amazing five billion units.

The technical importance of spark plugs

The spark plug, more than any other engine component, must demonstrate reliability and durability as a small, but crucial element in millions of vehicles the world over. Niterra’s NGK Ignition Parts brand has worked extensively to develop a product that is now not only more fuel efficient, but also offers unparalleled robustness over its lifetime.

And it is this quality that is crucial. The spark plug must ignite a mix of air and fuel between 350 and 9,500 times per minute within the combustion chamber of an engine in order to keep the vehicle’s wheels turning. To do this, the plug itself is screwed into the engine's cylinder head, with the upper part of the component presenting the electrical connection point. Depending on the engine’s ignition system, either the connector of the high-tension ignition cable is pushed onto this connection or – with more modern technical concepts – it may have its own individual ‘pencil’ ignition coil. The opposite end of the plug pushes into the combustion chamber and houses the spark electrodes. During an engine's operation, a high voltage is applied to the spark plug that creates an electric arc between the electrodes, which in turn ignites this air-fuel mixture. It is this simple, yet key function, that NGK brand has been perfecting for nearly a century and the reason why it is renowned for products that enable stable idle, superior antifouling properties, improved fuel efficiency and continued optimal performance.

A key component for every engine

Niterra’s NGK brand is a major spark plug supplier to both OE and Aftermarket and has pursued a path of continually perfecting its high-end products to make their service in the engines in which they perform more efficient.

As such a major manufacturer of spark plugs, ignition parts produced under the NGK brand cover almost all engine types available in the market. At the heart of the component is a centre electrode that is comprised mainly of nickel alloy. This crucial part provides the spark that passes to the earth electrode, itself made of nickel alloy on the standard NGK product. This part provides the opposite electrical pole to the centre electrode. NGK’s spark plugs provide excellent thermal conductivity, which helps prevent overheating and makes starting a vehicle that much more reliable.

Taking a step up, NGK’s precious metal plugs offer important performance advantages, with upgraded electrodes. Through the use of iridium, platinum or a mixture of both (in the case of the Laser Iridium range), these precious metal applications promise better cold starting, smoother idling, higher ignitability and improved fuel consumption. 

NGK’s premium product, the iridium spark plug, was introduced in 1997 and offers a harder wearing component that slots above the alternatives of platinum and nickel-based plugs.

While most spark plugs feature just one ground electrode, there are also multi-ground plugs that can have up to four ground electrodes.

The majority of modern spark plugs also feature a single ceramic insulator manufactured from aluminum oxide. This offers optimal heat resistance and consequently protects against overheating and mechanical shock. 

A closer look at these insulators on NGK’s vehicle plugs will also reveal the letter “R” in the part number. This denotes the presence of a resistor, which suppresses electromagnetic noise generated during the process of sparking. As this can interfere with electronic signals such as mobile phones and engine management systems, it is an important feature on NGK spark plugs. As well as investing heavily in research and development to keep its products to the highest technical standards, the brand has benefitted from many years of close collaboration with motorsports activities such as Formula 1 or MotoGP racing that has helped it ‘track test’ many of the new technologies that have found their way into consumer products. No surprise then that most of the world’s top automakers choose NGK spark plugs to power their vehicles. 

Parts of a NGK spark plug explained

A key factor of maintenance

In terms of changing spark plugs, it is always essential to consult the prescribed maintenance instructions. Automakers’ instructions on when to replace plugs can vary from 20,000 to 120,000 kilometres (12,500 to 75,000 miles), but again, iridium offers the best protection against erosion and therefore extends the life of such applications.

Generally, precious metal units will last longer than nickel plugs. This is reflected too in the longer service intervals required for iridium and platinum plugs.

As with any engine component, it is advisable to refer to a manufacturer’s instructions when fitting a new part. It is possible to exchange spark plugs yourself. But in order to obtain an optimal service life from plugs, proper attention must be paid to their removal, cleaning and replacement and the correct torque must be applied to seat them properly. Occasionally, problems can ensue, including carbon fouling. 

This occurs when the insulator surface gets covered by a substance such as fuel, oil or carbon, and as a result, misfires or fails to start. This can happen when plugs have been incorrectly fitted. Additional problems encountered by poor fitting of plugs can include lower-than-expected fuel economy.

Occasionally spark plugs will fail between replacement for reasons other than poor fitting. Generally, this is caused by overheating, the aforementioned buildup of carbon or another foreign substance, oil in the combustion chamber or an incorrect spark gap on the electrode. 


Hopefully this feature has provided some technical background into the NGK brand’s most famous product and its application in modern vehicles. This article is the first in a series to highlight the technical background of Niterra’s key automotive products. The next subject under the spotlight will be the glow plug, a part that helps power diesel engines.

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