Spark Plugs
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Spark plugs are essential components in your engine. Without them, your engine wouldn’t run. They work by generating a high-voltage spark that ignites the compressed air-fuel mixture in an engine's cylinder, producing the power needed to drive your vehicle.
Usually, you’ll find them in the cylinder head of an internal combustion engine. It’s fairly common for spark plugs to fail over time, so ensuring they’re routinely checked and replaced is essential for your vehicle’s performance and safety.
Buy spark plugs online or at your local Halfords
We’re one of the UK’s premier car parts suppliers. That means we have a huge selection of spark plugs online, with options available for various manufacturers and models. Every part, including spark plugs, is also available at 600+ Halfords stores and autocentres throughout the UK.
How spark plugs work
When an engine's piston (a moving part in the combustion chamber) compresses the air-fuel mixture in the cylinder, a spark plug delivers a precisely timed electric spark. This spark ignites the mixture, causing a controlled explosion. The explosion generates a powerful force that drives the piston down and converts chemical energy into mechanical energy, which powers your car and gets it moving.
Replacing spark plugs
When to replace your spark plugs depends on a few factors, including the type of spark plugs your vehicle uses, spark plug wear, the conditions you drive in, and your manufacturer’s recommendations. Most modern spark plugs are designed to last for a significant mileage range, typically between 30,000 and 50,000 miles.
Glow plugs
Glow plugs are heating devices used in diesel engines to aid in cold starting. Unlike spark plugs in gasoline engines, glow plugs do not create sparks. Instead, they heat up when electricity passes through them. This heat is used to warm the air in the combustion chamber, helping to ignite the diesel fuel more effectively in cold conditions.
Ignition coils
Ignition coils are electrical components in a vehicle's ignition system that transform low-voltage electrical power from the battery into high-voltage electrical energy. This electric jolt creates the sparks needed to ignite the gas and air mixture inside your engine's cylinders.
Spark Plug FAQs
Spark plugs are directly linked to your car starting and are an essential engine component that should be well maintained. If your car is misfiring or having problems starting, the chances are that it could be a problem with your car spark plugs.
Whether you’re a seasoned mechanic or not, locating the spark plugs in a combustion engine is fairly straightforward. Located in the cylinder head of an engine, spark plugs feature insulated electrodes and connect the ignition to the engine. As the spark plug detects electricity, the gap between the plug and the cylinder causes the voltage to transfer between the two points. A spark is then created which starts the combustion process. Typically, spark plugs require 20,000 volts to ensure the engine fires properly.
Once you’ve found the products you need, you can buy spark plugs using our convenient click & collect service to get hold of your products sooner. Or, if you’d prefer, try our trusted delivery service.We stock a variety of spark plug brands including Bosch, NGK, Denso and Beru. If you’re unsure of the best spark plug for your vehicle, our friendly colleagues can help.
Need help changing spark plugs? Don’t worry, just head down to your local Halfords Autocentre where one of our team will be happy to assist you. If you’re looking for advice on how to change spark plugs, check out our step-by-step guide.
Spark plugs typically need replacing based on a combination of factors, including the type of spark plugs, vehicle make and model, and driving conditions. As a general guideline, conventional copper spark plugs may need replacing every 20,000 to 30,000 miles, while platinum or iridium spark plugs can last up to 100,000 miles or more.
It's crucial to check your vehicle's owner's manual for manufacturer-specific recommendations and monitor for signs of wear like reduced fuel efficiency, rough idling, misfires, or difficulty starting the engine, which can indicate it's time to replace your spark plugs.
Our guide takes you through each step of fitting your new spark plug. Need a helping hand? Our trusted technicians can fit your spark plug on the very same day in Halfords garages up and down the UK.
Once you’ve found the products you need, you can buy spark plugs using our convenient click-and-collect service to get hold of your products sooner. Or, if you’d prefer, try our trusted delivery service. We stock a variety of spark plug brands, including Bosch, NGK, Denso and Beru. If you’re unsure of the best spark plug for your vehicle, our friendly colleagues can help.
Spark plugs vary depending on your vehicle's make, model and age. You should purchase the best spark plugs for your car for the best performance. To help you locate yours, we’ve designed a vehicle registration lookup tool that automatically pulls relevant products based on the registration number to suit your specific vehicle.
Spot oily spark plugs? Then, it’s a sign of an underlying problem. Start by removing the spark plugs and checking for oil deposits—issues like worn piston rings or damaged valve seals can often be the cause.
You’ll need to identify the root cause to fix oily spark plugs. This may involve replacing the faulty components, causing oil to leak into the combustion chamber. Once you've tackled the main issue, clean or replace the spark plugs, put them back in, and your engine should run smoothly again.
Regular maintenance of oil-related problems is paramount for safety and performance out on the roads. At Halfords, we provide a suite of car servicing options to keep your pride and joy running smoothly.
Since spark plugs assist in starting the engine, it’s likely that bad spark plugs will impact the engine through misfiring, surging or idling rough. Other signs to look out for include slow acceleration, high fuel consumption, or trouble starting the engine.
Over time spark plugs can wear out, with the average copper spark plug lasting 10,000 to 20,000 miles. Iridium or platinum spark plugs will last longer.
Spark plugs vary depending on the make, model and age of your vehicle. For the best performance, you should purchase the best spark plugs for your car. To help you locate yours, we’ve designed a vehicle registration lookup tool that will automatically pull relevant products to suit your vehicle based on the registration number.