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25 February 2025 Spark plug replacement and frequency
Your car's spark plugs may be small, but they play a big role in keeping your engine running smoothly. Over time, they wear out, leading to rough idling, poor fuel economy and even trouble starting your vehicle. Replacing them at the right intervals can improve performance and prevent costly repairs. But how often and how should you change them? Let's break it down so you can keep your engine in top shape!
How to change spark plugs: instructions
To change a spark plug, first, gather the necessary garage tools and ensure the engine is completely cool before beginning. Follow these steps for a smooth replacement:
- Gather tools and materials: You’ll need a socket wrench with a spark plug socket, extension bar, ratchet, gap gauge, dielectric grease, and new spark plugs for your car.
- Make sure the engine is cold: Wait at least 30 minutes after turning off the engine to avoid burns and ensure safe handling.
- Disconnect the battery: For safety, disconnect the negative terminal of the battery to prevent accidental electrical issues.
- Locate the spark plugs: Check your owner’s manual to find the spark plug positions, usually located along the engine’s top or side.
- Remove spark plug leads or coil-on-plug connectors: If your vehicle has spark plug wires, carefully pull them off by gripping the rubber connector, not the wire. For coil-on-plug systems, unplug and remove the ignition coil.
- Unscrew the old spark plug: Remove the old spark plug by carefully turning it anti-clockwise using the spark plug socket, extension, and wrench.
- Inspect and gap the new spark plug: Compare the old and new ones for wear. Use a gap gauge to check the gap size, adjusting if necessary per your manual’s specifications.
- Install the new spark plug: Thread the new plug in by hand to prevent cross-threading, then tighten with a wrench until snug, but avoid over-tightening.
- Reassemble the wires or coil-on-plug connector: Push the wires or ignition coil firmly back onto the new plugs. Ensure a secure connection.
- Reconnect and test the battery: Reconnect the battery, start the engine, and listen for smooth idling. If everything sounds normal, you’re good to go!
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How often do you have to change spark plugs?
You should replace spark plugs every 30,000 to 90,000 miles, depending on the make and model of your car. The interval between spark plug changes varies – copper plugs wear out more quickly, while iridium or platinum plugs last much longer. Not sure when to change your spark plugs? Check your owner's manual for the best schedule.
But don't just go by mileage – your car will tell you when it's time. If you're experiencing rough idling, sluggish acceleration, poor fuel economy or trouble starting, your spark plugs could be the culprit. Ignoring worn plugs can lead to misfires, poor performance, and even costly repairs.
A simple spark plug change can make your engine run smoother, improve fuel economy and keep your car running at its best. Stay ahead of the problems and change them before problems arise.
How many spark plugs are in a car?
The number of spark plugs in a vehicle depends on its engine configuration. Typically, internal combustion engines require one spark plug per cylinder. For instance, a four-cylinder engine will have four spark plugs, while a six-cylinder engine will have six.
High-performance vehicles with eight or more cylinders generally follow the same pattern, with each cylinder having its own spark plug. However, diesel engines and electric vehicles do not use spark plugs. Diesel engines rely on compression ignition rather than spark ignition, while electric vehicles use battery-powered motors that don't require any combustion process. This fundamental difference in ignition and propulsion systems eliminates the need for spark plugs in these vehicle types.
Where are the spark plugs located?
Spark plugs are strategically located in the car cylinder head of an internal combustion engine, within the combustion chamber. For optimum performance, they are usually centred between the valves, although this ideal placement isn't always possible in every engine design. In most engines, you'll find one spark plug per cylinder, but some models use two plugs per cylinder for improved efficiency.
-25%
Article number: 1496
compared to
RRP
£ 23,65
£ 17,73
Price per item
price incl. 20% VAT, excl. delivery costs
-58%
Article number: Z332
compared to
RRP
£ 24,01
£ 9,93
Price per item
price incl. 20% VAT, excl. delivery costs
Article number: 90911
£ 14,11
Price per item
price incl. 20% VAT, excl. delivery costs
-16%
Article number: 97098
compared to
RRP
£ 15,54
£ 12,99
Price per item
price incl. 20% VAT, excl. delivery costs
-25%
NGK Spark plug
M14 x 1,25, Spanner Size: 16 mm
Article number: 91898
compared to
RRP
£ 19,16
£ 14,29
Price per item
price incl. 20% VAT, excl. delivery costs
The spark plug's metal shell is screwed into the cylinder head and electrically grounded, while its central electrode protrudes through a ceramic insulator into the combustion chamber. This precise positioning ensures that the spark can effectively ignite the compressed air-fuel mixture, initiating the combustion process that powers the engine.
Is it easy to change spark plugs?
Changing spark plugs is generally straightforward for experienced DIYers, but some beginners may find it challenging. If you are comfortable with automotive maintenance, replacing spark plugs can be a manageable task. However, it requires some technical knowledge and the right tools.
Before you start, make sure the engine is cool and the vehicle is on level ground with the parking brake engaged. Access to spark plugs varies by vehicle model; some may require removing engine covers or other components.
Be sure to follow the manufacturer's guidelines for proper gapping and torque specifications. While not overly complex, this task demands attention to detail and careful handling to avoid damaging threads or other car engine components.
How long does it take to change spark plugs?
Replacing spark plugs typically takes 1–2 hours on a 4-cylinder engine, while V6 or V8 engines can take 2–3 hours or more. The complexity of changing spark plugs varies depending on the make and model of the car. Some cars have easily accessible plugs, making the job relatively straightforward for experienced do-it-yourselfers. Others, however, may require the removal of various components to reach the plugs, increasing the difficulty and time involved.
The correct tools, such as a spark plug socket, ratchet, and torque wrench, are essential. It's important to follow the manufacturer's specifications for clearance settings and torque values to ensure optimum performance and prevent damage. While experienced mechanics can complete this task with ease, if you are new to this, you should allow extra time and consider seeking professional assistance if unsure.
How much does it cost to change spark plugs in the UK?
In the UK, the cost of changing spark plugs tends to vary widely, depending on several factors such as the make and model of the vehicle, the number of spark plugs required and the type of spark plugs used. Labour costs also affect the overall price, with garages in rural areas generally charging less than those in urban centres, particularly London.
-51%
Article number: Z90
compared to
RRP
£ 12,91
£ 6,25
Price per item
price incl. 20% VAT, excl. delivery costs
-48%
DENSO Spark plug
M12x1.25,
Article number: VXUH20I
compared to
RRP
£ 31,83
£ 16,31
Price per item
price incl. 20% VAT, excl. delivery costs
BOSCH Spark plug
M 12 x 1,25, Spanner Size: 14
Article number: 0 242 129 510
£ 5,49
Price per item
price incl. 20% VAT, excl. delivery costs
BOSCH Spark plug
M 12 x 1,25, Spanner Size: 14
Article number: 0 242 140 565
£ 15,07
Price per item
price incl. 20% VAT, excl. delivery costs
-31%
NGK Spark plug
M14 x 1,25, Spanner Size: 16 mm
Article number: 94167
compared to
RRP
£ 33,67
£ 23,13
Price per item
price incl. 20% VAT, excl. delivery costs
Below is a table showing the average cost of replacing spark plugs for various makes of car. This information provides a useful reference point for estimating what you can expect to pay based on your vehicle. It's important to note that luxury brands often have higher service costs, while more common models tend to be less expensive to maintain.
|
Car Model |
Cost of Spark Plugs (£) |
Labour Cost (£) |
Total Cost (£) |
Notes |
|
Ford Fiesta |
25–35 |
50–70 |
75–105 |
Common model, affordable parts. |
|
Vauxhall Corsa |
20–30 |
45–65 |
65–95 |
Easy to access spark plugs. |
|
Volkswagen Golf |
30–40 |
60–80 |
90–120 |
Labour costs may be higher for some trims. |
|
Nissan Qashqai |
35–50 |
70–90 |
105–140 |
Often requires more time for replacement. |
|
Mini Cooper |
40–50 |
70–100 |
110–150 |
Performance plugs may cost more. |
|
BMW 3 Series |
50–60 |
80–120 |
130–180 |
Labour-intensive due to engine layout. |
|
Audi A3 |
40–55 |
80–110 |
120–165 |
Uses high-quality spark plugs. |
|
Toyota Yaris |
20–30 |
45–65 |
65–95 |
Affordable and straightforward process. |
|
Hyundai Tucson |
25–35 |
50–75 |
75–110 |
Routine replacement, moderate pricing. |
|
Kia Sportage |
25–40 |
55–85 |
80–125 |
Costs vary based on engine type. |
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