When to change spark plugs?

The automotive world is rapidly electrifying. However, despite how innovative electric cars are, the “old world” of internal combustion engines is also critically dependent on electricity. An internal combustion engine requires three components: fuel + air + spark. The spark in this equation is provided by plugs with a certain lifespan. When to change spark plugs? Let's try to answer this question.

How does a spark plug work?

When the engine is running, an electrical discharge generated by the ignition coil occurs between the side and center electrodes of the spark plug. The discharge has a high voltage of 25-30 thousand volts and ignites the fuel mixture. 

The heat generated by the combustion of the mixture raises the temperature, the pressure in the cylinder builds up, and the piston is pushed down. The movement of the piston is transmitted to the crankshaft and sets the car in motion. This process happens one at a time in each cylinder, and then it repeats until you turn off the engine.

Most engines have as many plugs as they have cylinders. That's why an inline four-cylinder engine has four plugs and a V-six has six. Some cars are indeed equipped with two spark plugs per cylinder for more accurate ignition.

Spark plugs are made up of many parts that utilize copper, nickel, iridium, and platinum, depending on the type of plug. Ceramics are also used in spark plugs for protection and insulation.

Why do spark plugs fail?

In the process, spark plugs become scaled, corroded, and reshaped, becoming less and less efficient. This is due to pressure, heat, and the chemical composition of the substances contained in the products of fuel combustion.

If you ignore the symptoms of malfunctioning plugs for a long time, any of them can fail. As a result, you can get a sagging power, difficulties with starting, and other, more serious malfunctions. To bring it to this, of course, you should not.

Types of spark plugs

There are three types of spark plugs on the market, which differ from each other in their materials of manufacture.

Nickel spark plugs

Considered the standard for most cars, these are the traditional type of spark plugs with a copper core and nickel alloy. Due to the larger electrode diameter, copper spark plugs are the largest, which means they require more voltage than other types to create a spark. Nickel alloy wears out faster than other metals, so these plugs usually need to be replaced every 30,000 km. But they are the most affordable spark plugs.

Platinum spark plugs

Similar to the previous ones, but instead of nickel alloy, a platinum disk is used in the center electrode. Due to their higher melting point and ability to withstand heat, platinum plugs wear out slower and can last up to 80,000 kilometers.

Iridium spark plugs

Iridium spark plug Denso ik20tt

Iridium spark plugs are considered to be of the highest quality due to their thin wire center electrode made of iridium, which is six times harder and eight times stronger than platinum. Although iridium spark plugs last longer than other types of spark plugs, they are also the most expensive.

When to change the spark plugs

The frequency with which spark plugs need to be changed depends on the material from which they are made. The table below shows the approximate life expectancy of spark plugs:

When to change the spark plugs

The frequency with which spark plugs need to be changed depends on the material from which they are made. The table below shows the approximate life expectancy of spark plugs:

Table

In reality, the life of the plugs depends on many factors, including fuel quality and the current condition of your engine. If your car comes with a service book, stick to the plug replacement dates specified in it. It is better to check the condition of spark plugs every 15,000 km.

Symptoms of spark plug malfunction

Signs that spark plugs need to be replaced:

Increased fuel consumption

Dirty spark plugs increase fuel consumption because the fuel mixture in part of the cylinders does not burn or burns inefficiently.

Slow acceleration

If acceleration takes longer and there is not enough power to overtake the car, it may be due to worn spark plugs. However, similar problems occur with a dirty fuel filter, clogged fuel injectors, and problems with the oxygen sensor and ignition system. All of these items need to be checked.

Uneven idle

The engine makes a noise like a beeping, grinding, or knocking noise, or there is a strong vibration.

Engine misfires

Pay attention to whether there is oil on the tip of the plug. It can be caused by a cracked valve cover gasket, destruction of the spark plug O-ring, cylinder head gasket, or defective or worn valve guides. Don't put off diagnosis for too long because oil can cause the engine to misfire or prevent it from starting. An engine that continues to misfire can damage the catalytic converter, which will cost about “mom-and-pop” dollars to replace.

Difficulty starting the engine

Trouble starting is the first signal to check the plugs. Other causes of difficult starting include problems with the ignition system, the need to replace the battery or frayed spark plug wires. 

Lights on the dashboard

Don't ignore the “Check Engine” light symbol or its counterparts located on the dashboard. They can signal a failing spark plug or that spark plug wires need to be replaced. For a complete list of events that cause the light to come on, refer to the owner's manual for your car model.