Spark plugs

Since 1959, DENSO has become one of the world’s leading pioneers of OEM quality spark plug technology

Spark plugs

How spark plugs work

Known as the ‘heart of the engine’, spark plugs play a key role in the ignition and performance of the entire engine. The well-timed combustion of the fuel-air mixture of gasoline and oxygen is what generates power in gasoline engines. The precise timing of the spark created by the spark plug ignites the fuel, triggering combustion.

To create this spark, a high voltage is passed between the centre electrode and ground electrode of the spark plug. This voltage breaks down the natural insulation between these electrodes and an electrical spark is generated. Although this strong spark only lasts for about 1/1,000 of a second, it has to be precisely and reliably timed to trigger the combustion of the fuel-air mixture.

Two DENSO TT spark plugs

Features and benefits

  • Optimum performance in a compact design.
  • Built by DENSO in-house, with ‘zero defects’ as standard.
  • Designs suitable for 90% of car models.
  • Developed in-house for a wide range of applications.
DENSO spark plug electrode close up
Expert technology development
Since our first design in 1959, we’ve been working to develop our spark plug technology and improve performance. This expertise informs the design of our huge range of compact spark plugs.
High, reliable performance
As engines downsize, spark plugs still need to provide similar or improved levels of spark performance. DENSO spark plugs provide the best optimum performance in a compact design.
Suitable for many applications
Our spark plugs are suitable for 90% of car models and are designed to provide reliable performance in a range of engine types and for various applications.

Types and characteristics

As well as designing to optimize performance, DENSO produces a range of spark plugs with different electrode shapes and sizes that are suitable for different engine applications.

Spark plugs types

Nickel TT®

As well as producing better ignitability than a Standard Nickel Plug, this is the first-ever fine-wired Spark plug without precious metal-based electrodes. The DENSO patented Twin Tip upgrade- technology is now available in the lower price segment. This means they’re available at a lower cost and are suitable for a wide range of applications. The technology provides a performance upgrade versus the normal nickel equivalent with average lifespan is up to 40.000km.

Iridium TT®

The two needle-thin electrodes in DENSO’s patented Iridium TT design enable sparks to grow 360 degrees in all three dimensions, improving ignition performance and combustion output, increasing spark plug lifespan and reducing emissions. The lifetime of these plugs meet any OE engine maintenance requirement. Performance is higher due to the Twin tip technology and the Denso patented 0.4mm centre electrode

Platinum Longlife

With platinum on both the centre and ground electrodes, these spark plugs are resistant to corrosion and erosion, meaning they can provide superior spark performance and lifetime on OEM level in excess of 60,000 km.

Iridium Longlife

With Iridium on the centre and Platinum chip on ground electrodes, these spark plugs are resistant to corrosion and erosion. These Denso Iridium Longlife plugs provide superior spark performance and lifespan according to the car makers requirements.

Iridium Super Ignition Spark Plugs (SIP)

Super ignition is considered the best available technology for spark plugs. Produced with Twin tip technology and a smaller centre electrode, DENSO’s super ignition spark plugs provide the highest levels of performance even within the most extreme and challenging environments. Super ignition spark plugs maintain a very long lifespan according to the car makers requirements.

Iridium Power

Specially shaped ground electrodes and a Denso patented 0.4mm diameter iridium centre electrode create high ignitability with low voltages. This compact design creates a 1.4% improvement in power output at 110km/h compared to normal plugs and is recommended for motorcycle engines.

Iridium Tough

This spark plug’s unique electrode design uses platinum, meaning it can provide powerful performance and improve fuel consumption on daily journeys for at least 100,000 km.

Iridium Racing

Designed with F1 performance in mind, the spark plug’s ultra-fine centre electrode creates fewer misfires, even in difficult conditions, providing unbeatable acceleration and ignition performance.



Catalogues and marketing materials

To find out more about Spark plugs browse the Downloads Area section. Click here.

Installation and fault finding

In order to find the right plug for your vehicle, you need to consider the heat range, hex diameter, total length and horsepower of the engine, as well as inspecting the condition of the current plug, to choose a new one accordingly.


Great care must be taken to ensure the safe installation of a spark plug:

To help you ensure accurate spark plug installation first time, please follow DENSO’s specifications below:


Fault finding

A spark plug’s appearance and various engine symptoms can help to diagnose damage:

Appearance: The insulator foot section and electrode section are covered with dried, soft black carbon.

Effects: Poor starting, misfiring, acceleration defect.

Cause: Repeated short-distance driving (driving with the engine cool), incorrect choking (overly rich air-fuel mixture), injection timing delay, plug heat range too high.


Appearance: The insulator section and electrode section are black and lustrous with wet oily deposits.

Effects: Poor starting and misfiring.

Cause: Oil leakage due to piston ring, cylinder, or valve guide wear (occurs easily to new engines and engines that have just been overhauled), high oil content in air-fuel mixture (2-stroke engines).


Appearance: The insulator leg section is scorched and extremely white with small black deposits. Rapid electrode wear.

Effects: Loss of power when running at high speed or under high load.

Cause: Spark plug incorrectly tightened, engine cooling problem, ignition timing too early, spark plug heat range too low, severely abnormal combustion.


Appearance: The centre electrode or ground electrode is melted or scorched. There are spots on the insulator leg section and deposits of aluminium or other metal powder.

Effects: Power loss due to engine damage.

Cause: Often this is due to overheating; pre-ignition is a phenomenon in which combustion occurs before ignition. The plug heat range is too low, the injection timing is too advanced, etc.


Appearance: The insulator leg section is cracked or broken.

Effects: Misfiring

Cause: Severely abnormal combustion, lack of attention to gap adjustment.