Spark Plug Replacement
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£152.78
Average cost for a spark plug replacement
Spark Plug Replacement
How much is a spark plug replacement?
A spark plug replacement costs £153.78 on average according to our data. This may differ depending on the make and model of your vehicle.
You can see the average price for some of the most popular car makes in the table below.
| Car Make | Average Price |
|---|---|
| Audi | £186.10 |
| BMW | £177.28 |
| Citroen | £130.11 |
| Ford | £126.69 |
| Honda | £139.18 |
| Hyundai | £141.35 |
| KIA | £132.55 |
| Mazda | £124.28 |
| Mercedes | £156.62 |
| MINI | £139.20 |
| Nissan | £178.76 |
| Peugeot | £170.68 |
| Renault | £143.65 |
| SEAT | £133.59 |
| Toyota | £121.34 |
| Vauxhall | £163.49 |
| Volkswagen | £137.41 |
Spark plugs are essential for petrol cars, providing (as their name suggests) the spark needed to start the engine. Like any component, they must be maintained to perform their job efficiently.
While spark plugs typically last between 30,000 and 90,000 miles, sometimes they wear out sooner than expected. If your car is struggling to start or misfiring, one of the most likely causes is faulty spark plugs. Fortunately, booking a replacement is easy, and it will only take a mechanic around an hour to complete.
Glow plugs
The average price of a glow plug replacement when booked on FixMyCar is £212.85. Glow and plugs are fundamental parts of your engine's system and help ignite and start your car. Your glow plugs need changing every 100,000 miles to ensure your vehicle runs smoothly.
Can include- Visual inspection and diagnosis
- Glow plug change
Car diagnostic test
The average price of a car diagnostic booked on FixMyCar is £51.66. Car diagnostic testing involves using special software to detect issues with your car's engine, electrical system, transmission, braking, exhaust system and more.
Can include- Full diagnostic testing
- Recommended repairs
Engine replacement
The average cost of an engine replacement when booked on FixMyCar is £429.45
In some circumstances, you may need a complete engine replacement. A professional will tell you if this is necessary or if other repairs may act as an effective solution.
Can include- Testing and inspection
- Engine replacement
How do spark plugs work?
Spark plugs create a high-voltage spark in the cylinder head, igniting the mixture of fuel and air in the combustion chamber. They have an insulated central electrode connected to an ignition coil by a heavily insulated wire, forming a spark gap inside the cylinder.
In addition to igniting the air-fuel mixture, they also have a secondary purpose. Contrary to what you might expect, spark plugs cannot create heat; they can only remove it. They work as heat exchangers by transferring thermal energy from the combustion engine to the cooling system.
How often to replace spark plugs
Different spark plug materials have different lifespans and need to be replaced at varying intervals. Classic spark plugs typically last around 30,000 miles, platinum spark plugs last about 55,000 miles, and high-end iridium spark plugs may last 100,000 miles or more.
This guide provides an overview of the types of spark plugs and how to change them.
A good rule of thumb is to check the recommended usage of your spark plugs - information that should be available from the manufacturer - and replace them at this interval, even if you haven’t experienced any symptoms suggesting they are worn.
Signs you need your spark plugs replacing
Look out for the following signs that your spark plugs need to be replaced.
Your car struggles to start
If your car often stalls when you try to start it, this is a classic sign your spark plugs are worn out because they are no longer capable of creating a spark to start the engine. There could also be a problem with the spark plug wires. However, if your car won’t start at all, the battery is probably to blame.
This guide discusses other reasons your car might be stalling.
Your car struggles to accelerate
Worn-out spark plugs can hamper the performance of your vehicle, leaving it feeling sluggish. If your car is less responsive when you put your foot down, it might be time for a new set of spark plugs.
The check engine light is on
Car warning lights should never be ignored - this guide explains what they mean. Often, the check engine light signals a problem with the spark plugs when they fail to ignite the air and fuel in the chamber. The light may stay on permanently or flash.
A flashing check engine light could indicate serious misfires in the engine, which could cause irreparable damage to the catalytic converter. That’s why it’s best to replace your spark plugs as a regular part of car maintenance rather than waiting for them to fail.
There are other reasons your engine management light may come on, as we discuss here.
Rough idling
Take a moment to listen to your engine. If you notice any unusual rattling, knocking or pinging noises or if your RPM seems to jump up and down, your spark plugs could be to blame.
Poor mileage
Most drivers have a rough idea of how long a tank of fuel usually lasts. Faulty spark plugs often have a knock-on effect on fuel efficiency - when your car starts guzzling gas, it might be time to replace them.
Misfiring
Engine misfiring happens when the combustion reaction fails, and the cylinder doesn’t fire. As a result, your car may seem to stumble and lose speed. Find out more about engine misfiring and why it happens here.
Check out this guide for additional advice about diagnosing common car problems.
Benefits of replacing your spark plugs
Numerous benefits come with following a spark plug replacement schedule:
Increased engine performance and efficiency
Better fuel economy
Smoother acceleration
More responsiveness
Reduced emissions
Fully-functioning combustion process
Reduced risk of engine damage from misfiring
Your owner’s manual should specify how often your spark plugs need replacing, and this job may be included during a full service.
Which spark plugs for my car?
Take a look at this guide for a detailed overview of the types of spark plugs that are available and which is best for your car. Your vehicle handbook should also contain information about recommended spark plugs.
Which spark plugs last the longest?
The longest-lasting spark plugs are made from iridium, which is eight times stronger and six times harder than platinum, the second longest-lasting spark plug material. Copper spark plugs are the cheapest and most common type, though they are the least durable.
Where are spark plugs located?
You can locate your car’s spark plugs by looking for a collection of four to eight wires under the bonnet. They lead to various engine parts with a spark plug at each end, usually protected by covers.
Many cars have engine covers that must be removed to access the spark plug wires. In four-cylinder engines, the spark plugs are usually in a row on the side or top of the engine; inline six-cylinder engines often have spark plugs on the top or side of the engine head; and in V6 and V8-cylinder engines, they are usually split evenly at either side.
You can find this information in your vehicle handbook, which will also provide information about the type and size of spark plugs your car requires.
Do all cars have spark plugs?
Only petrol cars have spark plugs; diesel engines use glow plugs instead. Find out the differences between spark plugs and glow plugs in this guide.
How do I know if my spark plugs need changing?
These five symptoms suggest your spark plugs may need replacing:
Engine misfiring
Check engine light
Rough idling
Car struggles to start and accelerate
Decreased fuel efficiency
Learn more about identifying spark plug problems here.
Can you drive with bad spark plugs?
Driving with worn-out or damaged spark plugs could cause serious engine damage. For this reason, it is not recommended.
Replacing your spark plugs will be much cheaper and easier than repairing the damage they cause when they’re not working correctly, especially since they may harm your catalytic converter, which is expensive.
