Facts to consider when choosing the spark plugs

Facts to consider when choosing the spark plugs

Petrol engines use spark plugs for igniting the air-and-fuel mixture inside the cylinders. They differ in the number of electrodes, production material and are produced by a wide range of companies. In this article, you will find information on how to choose the components properly to make the engine start easier, increase its output, reduce fuel consumption, and many other useful tips.

Main types

 By the number of electrodes: 
  1. Single-electrode. They have one centre and one side electrode made of metal with a diameter of 2.5 mm. This simple design ensures efficient combustion. Such parts are low-priced and have a short working lifespan.
  2. Multi-electrode. They have up to 4 side electrodes. They feature high longevity because their working elements wear out one by one. However, it is impossible to adjust the gap between the electrodes. These components are the best choice for engines in which the spark plugs wells are hard to reach.
Spark plugs single-electrode, multi-electrode.
 By production material of the centre electrode (we list only the most common types): 
  1. Copper-nickel. They have a working lifespan of 25,000-30,000 kilometres. They are affordably priced and optimal for in-line engines.
  2. Platinum. They serve for up to 120,000 kilometres. They feature a thin electrode, which emits a more powerful spark.
  3. Iridium. These plugs are more resistant to high temperatures and corrosion. They have the same lifespan as the platinum ones and provide maximally efficient fuel combustion.
  4. Silver. They are resistant to high loads, vibrations, as well as to fouling. They are the best choice for cars working on liquefied petroleum gas. Their disadvantage is a short working lifespan: on average, up to 30,000 kilometres.
Spark plugs copper-nickel, platinum, iridium, silver.
A tip from AUTODOC: Platinum and iridium components are relatively expensive. However, if your car has hard-to-reach spark plugs, it is better to install parts of these types, as they feature a long working lifespan. The same advice goes, if your car sees a lot of use. In other cases, you could do with budget components perfectly.
 By heat range: 
  1. Hot. They have low heat dispersal from the central electrode and insulator. They are used in power units with a low compression ratio, operating on low-octane fuel.
  2. Cold. They feature high heat dispersal and are used in motors that require high-octane fuel and have a high compression ratio.
  3. Medium. They have balanced characteristics of the first two types. These spark plugs are the most common.
Spark plugs hot, cold, medium.
Apart from this, spark plugs differ in diameter, thread pitch and length, size of the hex socket and sealing type (a soft-metal washer or conical seat).

Popular models of spark plugs

  • Bosch Platinum plus HR6DP. They have a central electrode with a soldered platinum tip. They are extremely wear-resistant and have a long working lifespan – up to 120,000 kilometres of mileage.
  • Denso K20TT. They have thin 1.5 mm electrodes made of nickel. They are suitable for power units operating on petrol as well as on liquefied petroleum gas. They have similar characteristics to the iridium plugs but are more affordable. These spark plugs reduce fuel consumption and exhaust emissions.
  • Champion N9BYC4. They have three ground electrodes and long service life – up to 70,000 kilometres of vehicle mileage.
  • Beru ULTRA-14FGR6DDU. Their peculiarity is two pairs of asymmetrical additional electrodes. Their operation is stable even at low voltage.
  • Valeo R76H11. They have one side electrode and an optimal spark gap, which ensures perfect spark formation. As a result, less fuel is consumed and some engine power increase occurs (up to 2.1%). They have an affordable price.


Replace the spark plugs, if their working lifespan has ended. Ignoring this problem for long can lead to a breakdown of the engine and other vehicle systems. Follow AUTODOC’s recommendations and install the components that suit your car best.


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