How and when to change spark plugs in the car

How often should I change spark plugs?

Frequency of spark plug replacement depends primarily on their type, more specifically, the material of the central electrode, as well as the vehicle operating conditions, fuel quality, timeliness of oil changes, the presence of interruptions in the engine and other external factors. The service life of the nickel plugs is 45 000 km, the platinum ones – 80 000 km and the iridium ones – 120 000 km. In practice they fail 1.5-2 times quicker. The average interval for changing spark plugs is 30-60,000 km.

Read our article about how often you need to change spark plugs, what signs indicate the need for immediate replacement and what can happen if you don’t change spark plugs on time.

Why change spark plugs

Why change spark plugs, check on the stand: video

The function of the spark plug is to ignite the fuel-air mixture (FAM) formed in the engine cylinders. When all systems are working properly and parts are in perfect condition, ignition occurs at a precise moment in time through a spark discharge from the air gap between the center and side (lateral) electrodes. The resulting energy sets the piston in motion, thus the engine’s performance directly depends on the serviceability of the part.

The need to replace spark plugs is due to the fact that they are subject to natural wear due to spark erosion, temperatures up to 2500 ℃ and pressures up to 50 bar in the combustion chamber, as well as the effects of aggressive substances contained in the combustion products. As the electrodes are deposited, thinned and melted, which leads to an increase in the gap, changes in the shape and power of the discharge up to the periodic or permanent absence of spark.

With each 1000 km traveled the gap between the electrodes of the classic nickel plug increases by 5-10 microns.

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Ideally, it is necessary to change spark plugs before there are obvious visual signs of wear and characteristic its symptoms:

  • Difficulty starting the engine; ;
  • deterioration of acceleration dynamics;
  • increase in fuel consumption;
  • appearance of errors P0300-P0304, indicating ignition skips.

These symptoms may also occur when there is a loss of spark due to faulty ignition coils, high-voltage wires, and in carburetor models – when the ignition distributor is faulty or misadjusted.

Following the manufacturer’s recommended interval for replacing spark plugs by mileage, taking into account the operating conditions, will avoid these problems and the more severe consequences to which ignition system malfunctions lead.

What happens if you don’t change the plugs in your car

Violating spark plug replacement intervals and ignoring signs of spark plug wear can eventually lead to more unpleasant consequences. The most serious problems you can encounter if you don’t change the spark plugs in your car on time are listed in the table below.

Problem Cause Consequences
Detonation ignition An inconsistent, untimely or insufficiently powerful discharge leads to an explosive ignition of the fuel-air mixture in the combustion chamber. The shock wave has a destructive mechanical effect on the pistons, connecting rods and crankshaft. The resulting temperature increase can burn through valves, pistons and cylinder-head gaskets.
Caliche ignition Fuel injection is ignited by red-hot electrodes, not a spark. Increase of pressure and temperature leads to burnout of parts of cylinder-piston group and formation of burrs on the cylinder walls.
Injection of FAM into the exhaust In case of ignition failure, the unburned fuel-air mixture together with the exhaust gases enters the exhaust manifold. The toxicity of the exhaust increases, the wear of the catalytic converter is accelerated, and if the FAM is ignited in the exhaust, its destruction may occur as a result of the shock wave (you may hear popping sounds in the exhaust pipe).
Spark plug destruction Damage to the electrodes and insulator as a result of critical mechanical or thermal wear during operation and during replacement. Chipped electrodes or insulator elements left in the combustion chamber cause damage to the piston and cylinder walls.
Significant increase in discharge voltage Increased resistance due to increased electrode gap or deposits on the electrode surface, possible breakdown of coil insulation or BB wire tip. Failure of ignition coil and/or high-voltage wires.
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You may also encounter the problems listed in the table if the spark plugs are installed with the wrong caliber or gap, or if low-quality or counterfeit parts are used.

When to change spark plugs

When best to change spark plugs: video

How often it is necessary to change spark plugs in the car – depends on their design features and the operating conditions of the car, the quality of fuel and engine oil, as well as the state of other components of the ignition system and the correctness of its adjustment. The most correct approach is to determine the frequency of replacement of spark plugs by a combination of the following factors:

  • material of the center electrode;
  • the number of side electrodes;
  • intensity and duration of travel;
  • driving style;
  • type and quality of fuel.

Determining that it is time to change spark plugs just by mileage or by signs will lead to unnecessary costs.

At what mileage to change nickel, platinum and iridium spark plugs

The type of spark plugs is determined depending on the material from which the center electrode is made, and more specifically, its tip. In the simplest and cheapest parts, it is made of a nickel alloy, while the more expensive ones use platinum and iridium. It is this feature that is key in terms of spark plug life.

The average life of plugs with nickel, platinum and iridium electrodes is shown in the table.

Type of plug Average lifetime per standard, km
Nickel 45 000
Platinum 80 000
Iridium 120 000

Note that the service life of a particular manufacturer’s spark plugs may vary by 15% up or down depending on other design features.

The extended replacement interval of platinum and iridium plugs is due to the higher thermal conductivity of the precious metals, which reduces the electrode temperature. In addition, the properties of the materials allowed to reduce its thickness to 0.4-1 mm, which had a favorable effect on the formation of the discharge and reduced the wear of the electrodes themselves from the spark erosion. The service life of nickel plugs is shorter precisely because their electrode is more prone to melting and edge wear.

How often should multi-electrode spark plugs be replaced?

Multi-electrode spark plugs

Spark plugs of classical design have only one electrode on the side. Along with them there are products with one, two or three additional electrodes. Contrary to popular belief, this particular feature has almost no effect on the ignition efficiency, but does increase the life of the part. The spark discharge is formed only once – between the central electrode and the least worn side electrode, choosing the path with the minimum resistance.

The service life of multielectrode spark plugs is not proportional to the number of electrodes, but still about 20-30% longer than that of conventional plugs of the same type. Such parts are well suited for models with an idle spark ignition system. In this case, a single coil simultaneously charges two spark plugs – one ignites the mixture during the compression stroke and the other fires idle during the exhaust stroke.

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How the spark plug change interval is affected by the operating conditions

The recommended spark plug replacement interval by mileage in the vehicle owner’s manual and the life on the package are given for ideal conditions. This can be taken into account as the maximum, after which the part must definitely be replaced. In practice, its characteristics usually deteriorate much earlier.

What shortens the service life of spark plugs:

What affects the service life of spark plugs and recommendations for replacement: video

  • frequent cold starts and trips of up to 30 km;
  • driving in heavy traffic and at engine speeds of 2,500 rpm or less;
  • sudden starts from a place, revolutions up to “cut-off”;
  • low fuel quality;
  • untimely replacement of oil and air filter.

With short runs and low RPMs the plug doesn’t warm up and has no time to self-clean. As a result, a deposit of sulfur, phosphorus and other aggressive substances in fuel and oil is formed on its surface, contributing to accelerated corrosion and preventing spark formation.

Carbon deposits on electrodes and insulators can also appear during normal operation due to poor-quality fuel with foreign additives, old oil, too lean or too rich fuel-air mixture. Excessive driving reduces the service life of the spark plugs due to the high temperature in the combustion chamber and the high frequency of discharges.

How to know when it’s time to change spark plugs

It is impossible to determine exactly how often it is necessary to change spark plugs, because the operating conditions of each car are individual. It is necessary to orient, first of all, on the service interval specified in the manual or service book of the car, taking into account difficult conditions. Practice shows that if the car is regularly serviced and driven near optimal conditions, quality nickel spark plugs have a service life of 30-40 thousand km, platinum – 50-60 thousand km, and iridium – 80-100 thousand km.

Since not all factors affecting the service life of plugs can be considered and identified, it is advisable to remove and inspect them every 15,000 thousand kilometers. This will not only allow you to detect signs of wear in time, but also perform a preliminary diagnosis of the engine by the color of the soot.

Cracks in the ceramic coating of spark plugs

Visual signs that indicate the need to replace the plugs :

  • A noticeable change in the shape or damage to the electrodes, especially the center electrode;
  • Cracks or other defects on the insulator;
  • Thick, velvety or varnished deposits of any color;
  • abundant black soot on the outside of the insulator in the area of the coil or lead wire cap.

A visual difference between one spark plug and the others, thicker soot, oil or fuel on the plug should alert you. It indirectly points to problems with the engine, ignition system or combustion system, but the cause of ignition failure may be the spark plug itself. Only a check will tell you if this is the cause.

Normal spark plugs have no visible difference from new ones except for a thin, easy to remove light brown or grayish residue. A brown ring about 1 cm wide on the outside of the insulator is also not a sign of malfunction. It is just a corona discharge trace, that is, dust and oil particles drawn to the insulator and deposited on it.

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Do I have to change plugs when switching to gas

Plazmofor Super yttrium spark plugs for mixed gas and gasoline cycles

The gas-air mixture is poorer than the gasoline-air mixture, burns longer, which leads to higher temperatures in the combustion chamber, but at the same time burns cleaner. Because of these peculiarities, it is usually recommended to replace the spark plugs with more suitable ones when installing HBO.

It is worth noting that there are no so-called special spark plugs for gas. The parts recommended for installation in conjunction with HBO are cold spark plugs with platinum, iridium or silver electrode and reduced to 0.7-0.8 mm gap. They can also be used for an engine that runs on gasoline, especially since in most cases, starting and warming up takes place on this fuel, even in the presence of HBO.

Quality platinum or iridium plugs can be not changed when switching to gas. They resist heating quite well and provide stable ignition of denser gas-air mixture. But it is better to change the nickel ones for more suitable ones – their ignition efficiency will be lower, and the electrodes will quickly become useless. However, if you are ready to change spark plugs every 10-20 thousand km run, and you do not consider a slight loss of dynamics as a problem, you can leave them.

Frequently Asked Questions

What is the service life of spark plugs?

The average life of nickel spark plugs is 45, platinum – 80 and iridium – 120 thousand km. In practice, due to the difficult operating conditions and poor fuel quality, they serve 1.5-2 times less.

What will happen if you don’t change spark plugs for a long time?

In the initial stage, untimely replacement of spark plugs can lead to hard cold starting of the engine, loss of dynamics and increased fuel consumption. If they continue to be used, detonation, glow ignition, ignition skips and ignition of the fuel-air mixture in the exhaust may occur, which can lead to the failure of the elements of the exhaust system and engine.

What will a spark plug replacement do?

Regularly changing the spark plugs ensures the efficient functioning of the ignition system, easy starting and stable engine operation, compliance with the factory fuel consumption and acceleration dynamics.

Do I need to change spark plugs for the winter?

Spark plugs do not need to be changed for the season. Changing them for winter makes sense only if they are nearing the end of their service life or there are obvious signs of wear. A cold start will be difficult in this case. The ambient temperature does not affect the operation of the plugs, but the humidity may also have an impact, if there is a breakdown of the insulator.

How often should I change the spark plugs on gas?

With a qualified SBS setting, the use of quality fuel and proper selection of spark plugs on gas, they last as long as those on gasoline. As a result of prolonged combustion of the mixture, they almost do not form soot, but hot spark plugs can wear out faster due to exposure to high temperatures.

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What happens if … not change the spark plugs, but how long do you change the plugs?)

For many motorists, the question of when it is better to change spark plugs – in the time period recommended by the manufacturer of the car or the plugs themselves or judging by their actual condition, is the same stumbling block, as well as whether to drive on 92 or 95-m gasoline. Some proprietors of a car strictly adhere to regulation terms, considering that the producer of the car knows better, when it is better to replace this expendable element. Others think that since the spark plugs are in good condition and the engine fires up without a hitch even in severe frost, they should be changed not earlier than 60-90 thousand km run. Let’s analyze what may happen to your car, if you do not change the spark plugs within the manufacturer’s specified terms.

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Why does the engine need spark plugs?

To begin with, let’s remember what function the spark plugs perform in the engine. These devices are needed to ignite the fuel-air mixture in the combustion chamber (cylinder) of the engine. This mixture is ignited by an electrical discharge of several thousand or tens of thousands of volts between the electrodes of the spark plug.

A standard spark plug consists of several components:

– A contact lead (designed to connect the spark plug to the high-voltage wires of the ignition system or directly to the ignition coil);

– insulator (protects the spark plug from overheating, the part of the insulator directly adjacent to the center electrode, most strongly affects the quality of the spark plug);

– ribs of the insulator (prevents electrical breakdown on its surface)

– central and lateral electrode (it is between them that a spark is created, igniting the fuel-air mixture in the cylinder);

– gasket (serves to prevent penetration of hot gases from the combustion chamber).

An important characteristic of any spark plug is the gap between the center and side (side) electrodes. This is what determines how effectively the mixture in the cylinder will be ignited. The larger the gap, the more powerful the spark and the larger the ignition zone. Accordingly, the fuel will burn more efficiently, and, consequently, its consumption will be stable and the engine will run smoothly. On the other hand, when the gap between the spark plug electrodes is smaller, the spark appears earlier and the breakdown occurs at a lower voltage. But at the same time the spark energy is less, which is worse for the mixture ignition, and eventually with a reduced gap the power and fuel efficiency of the engine is reduced.

Also an important characteristic of plugs is their glow number – this is information about the maximum allowable temperature load of the spark plug. Domestic spark plugs are available with a glow number of 8, 11, 14, 17, 20, 23 and 26. Foreign manufacturers do not stick to a single scale of glow numbers. Depending on the value of the glow number candles are divided into “cold”, “hot”, the average and unified. If you put too “cold” plugs (with a high ratio), hinder the self-cleaning process, and the engine will run out of juice. If too “hot”, the so-called glow ignition is possible, resembling an engine detonation in its symptoms and destructive consequences.

What kind of plugs are there?

In common usage, spark plugs are called classic, platinum and iridium spark plugs.

They are so called because of the materials that are used to manufacture the electrodes. In the classic candles electrodes – copper, in the platinum candles are made of platinum, and iridium – from a special iridium alloy. In some classic plugs, the copper electrodes are coated with an yttrium alloy for reliability, which increases the stability of the electrodes of the plugs. Platinum candles are good because platinum has a high corrosion resistance and resistance to high temperatures (almost does not burn out), which allows for a fairly long service life. Iridium candles have similar characteristics to the platinum ones. But the most durable candles are those in which the electrodes are made of an alloy of platinum and iridium.

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The service life of candles depends on many factors. Manufacturers determine the life of these elements depending on the materials from which the electrodes are made, the approximate operating conditions (climatic conditions, fuel quality and others). For example, for classic spark plugs, the average service life is no more than 50 thousand kilometers of mileage. For platinum and iridium – not more than 90 thousand kilometers. Naturally, these figures may be adjusted depending, for example, on the quality of gasoline you pour into the car and the condition of the engine itself. Therefore, many car manufacturers recommend replacing classic spark plugs at the passage of every other scheduled maintenance service (for example, after 30 and then 60 thousand kilometers). When using platinum or iridium spark plugs, the service life may be increased by one and a half to two times.

What happens if the plugs are not changed in time

Suppose, for some reason, the due date of replacement of spark plugs has expired, and the owner of the car did not bother to install new elements. Probably, it will not lead to any tragic consequences for the engine of the car at once. But one day the car will not start. Therefore, we advise you to pay close attention to the signs indicating the soonest failure of spark plugs.

Signs of spark plug failure include:

– “thrashing” of the engine (it jerks when driving and at idle speed)

– Difficulty in starting the engine (starter engages, but ignition does not occur)

– increase in fuel consumption

– increase in CO

– engine dynamics worsening (the engine does not reach its maximum speed and its output diminishes)

If you ignore the above signs, the engine may fail.

One of the unfortunate consequences of faulty spark plugs can be detonation in the engine combustion chamber. Detonation of a certain volume of mixture results in a shock wave, which, depending on the volume of mixture, may be of such intensity that its energy will make all the remaining charge in the cylinder detonate. When the shock waves are reflected from the wall of the combustion chamber, a ringing metallic sound is produced. With a strong detonation, the knocking becomes louder, the engine output drops, and black smoke appears in the exhaust gases. Also during a strong detonation, the engine experiences high thermal and mechanical stress on some parts. Piston edges and cylinder head gaskets and spark plug electrodes can get burnt. Shock waves destroy the oil film at the top of the cylinder, thus causing increased wear.

– You should install the spark plugs recommended by the manufacturer, paying attention to their caliper number and other characteristics

– In spite of the stable operation of the ignition system, the condition of the spark plugs should be checked at each scheduled maintenance

– long service (run of 50 thousand kilometers and more) is possible with the installation of spark plugs with platinum or iridium electrodes

– To extend the service life of plugs you need to fill only a proven fuel if possible, change filters on time, monitor the correct setting of the gap glow plugs

– If you see signs of plug failure (“tripping” of the engine, increased fuel consumption, “floating” speed), urgently contact the service station or independently replace these elements for new ones.

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