Car spark plugs – what are they and how do they work?

Spark plugs are one of the most important components in any gasoline engine. They ensure that the fuel and air mixture in the cylinder ignites at the right moment and with sufficient force. Without properly functioning spark plugs, your car will not start, lose power, or use more fuel.

In this article, we'll explain how spark plugs work, what types there are, when to change them, and what symptoms indicate wear .

What is a spark plug ?

A spark plug is a device located in an engine that creates an electrical spark to ignite the fuel-air mixture in the cylinder.

Each cylinder has its own spark plug, and they work together with an ignition coil, which generates high voltage to create a spark between the electrodes of the plug.

How does a spark plug work?

1. The ignition coil generates high voltage (up to 40,000 V).

2. High voltage travels to the center electrode of the spark plug.

3. A spark is generated between the electrodes , which ignites the fuel-air mixture.

4. The explosion pushes the piston down – this is how the engine's power is created.

Precise timing plays a big role. Even a small error in the ignition timing can affect engine performance.

types of spark plugs

1. conventional nickel electrode spark plugs

• cheapest

• shortest lifespan (20,000–30,000 km)

2. iridium spark plugs

• very thin electrode, more precise spark

• long life (60,000–120,000 km)

• the best choice for most modern gasoline engines

3. platinum candles

• more durable than nickel

• moderately priced, with average service life

4. multi-electrode spark plugs

• more electrodes ensure better ignition in all situations

• more resistant to impure fuel

Why are spark plugs so important?

A good spark plug ensures:

• smooth engine operation

• lower emissions

• lower fuel consumption

• better acceleration

• easier cold start

bad spark plugs cause everything the opposite.

Symptoms of worn spark plugs

When spark plugs start to get tired, the car will give you a pretty clear indication:

• Uncertain idle (engine "shakes")

• difficult starting , especially in cold weather

• loss of power and poor acceleration

• increased fuel consumption

• occurrence of engine failures (misfire)

• check engine light

If you notice any of these symptoms, it's a good idea to check or replace the spark plugs.

When should you change spark plugs?

The replacement interval depends on the type of spark plug:

candle type	recommended replacement interval
plain nickel	20,000 – 30,000 km
platinum	40,000 – 60,000 km
iridium	60,000 – 120,000 km

Note: some modern car manufacturers allow up to 160,000 km with iridium spark plugs, but in Estonian conditions it makes more sense to change earlier.

What to consider when choosing spark plugs?

• follow the type and size recommended by the car manufacturer

• Incorrect heat range can cause overheating or sooting

• cheap and unknown brands can be dangerous for the engine

good practice:
use NGK, Denso, Bosch, Champion or other well-known manufacturer.

Can you change the spark plugs yourself?

Yes – on many cars it is easy. But you need to pay attention:

• using the correct torque values

• do not twist the candle too hard

• clean the candle sockets

• check the condition of the ignition coils

If it seems complicated, it's worth having a specialist do it - the work is not expensive and reduces the risk of failure.

You can find the spark plug wrenches needed to change spark plugs here!

summary

Spark plugs are small in size but extremely important parts in the operation of a gasoline engine. Properly functioning spark plugs ensure:

• powerful and clean combustion

• stable engine operation

• lower fuel consumption

• longer engine life

Regular replacement and using high-quality spark plugs is the best way to keep your car economical, powerful and reliable.

You can buy new spark plugs for your car here!