How often should you replace spark plugs?

Your car’s spark plugs are essential for smooth engine performance, and understanding them can help you avoid costly issues. Here’s everything you need to know about spark plugs – and when to replace them.

Think of your car’s spark plugs as the tiny sparks that keep your engine alive. They ignite the fuel-air mix, powering your car and keeping it running smoothly. When spark plugs wear out, your engine can misfire, struggle to start, or guzzle more fuel than it should.

Like anything under your car’s bonnet, spark plugs don’t last forever. Heat, friction, and engine deposits take their toll over time, and factors such as your driving habits, engine type, and spark plug quality all play a role in how long they’ll perform.

This handy guide explains how long spark plugs usually last, what speeds up their wear, and the key signs it’s time for a replacement – helping you avoid costly engine troubles and keep your car running like new.

Remember, you can buy a brand new or used car right here on Carwow. And you can sell your car, too. We’re here to help you through every step of your car-changing journey.

What does a spark plug do?

A spark plug’s job is simple but vital: it creates the spark that ignites the fuel-air mixture in your engine, powering your car. Think of it as your engine’s tiny ignition switch. Spark plugs also help manage engine heat, keeping everything running smoothly and efficiently.

How long do spark plugs last?

Spark plugs usually last anywhere from 30,000 to over 100,000 miles, depending on the type. Copper spark plugs wear out fastest, around 20,000-30,000 miles, while platinum and iridium plugs can keep your engine running smoothly for 60,000 to 100,000+ miles.

What affects the lifespan of a spark plug?

The lifespan of your car’s spark plugs can be affected by these six key factors:

1. Spark plugs made of platinum or iridium are highly durable and wear-resistant, making them ideal for high-performance engines. Copper and nickel plugs, on the other hand, are more affordable but wear out faster.
2. Short trips prevent the engine from reaching optimal temperature, causing carbon buildup (fouling) and reducing efficiency. Stop-and-go driving also speeds up wear.
3. A healthy engine helps spark plugs last longer. Oil leaks, improper air-fuel mixtures, or cooling system issues can drastically shorten their life.
4. Low-quality fuel or oil with additives can leave deposits on the electrodes, leading to fouling and reduced performance.
5. Extreme engine temperatures and high-pressure shocks can damage the spark plug’s insulator, affecting its effectiveness.
6. Incorrect installation can crack the insulator or cause poor performance, reducing the plug’s lifespan.

Signs you’ve got worn spark plugs

Keep an eye out for these six signs that your spark plugs may be wearing out:

1. Engine misfires: Your engine may hesitate or jerk during acceleration, indicating the spark plugs aren’t igniting the fuel-air mix properly.
2. Difficulty starting the car: Worn spark plugs can make it harder for your engine to start, especially in cold weather.
3. Poor fuel economy: If your car is using more fuel than usual, worn plugs may be causing inefficient combustion.
4. Rough idling: A shaking or uneven idle (when the engine is running while stationary) can signal that spark plugs aren’t firing consistently.
5. Loss of power: You might notice slower acceleration or reduced overall engine performance.
6. Unusual engine noises: Popping, pinging, or knocking sounds from the engine can indicate spark plug problems or misfires.

What happens if you ignore a worn spark plug?

If you ignore worn spark plugs, your car may start giving you signs like those discussed above. Over time, this neglect can lead to serious and expensive damage – such as a failing catalytic converter, damaged ignition coils, or even complete engine failure.

How much does a spark plug replacement cost?

Replacing all the spark plugs in your car can cost anywhere from £50 to £500. The final price depends on your vehicle’s make and model, the quality of the spark plugs, and any labor charges from a trusted local garage.

On average, replacing a single spark plug costs around £153, says WhoCanFixMyCar. Here are some average replacement costs you can expect to see depending on the car brand, according to the car repair network site:

Car manufacturer	Average replacement cost
Audi	£186
BMW	£177
Ford	£126
Honda	£139
Kia	£132
Mercedes	£156
Nissan	£178
Peugeot	£170
Toyota	£121
Volkswagen	£137

Spark plug FAQs

Can I replace a spark plug myself?

Yes, in many cases you can replace your own spark plugs. It’s a fairly simple DIY job if you have the right tools and your engine is easy to access.

Here’s the equipment you’ll need:

• A ratchet and extension
• A spark plug socket
• A spark plug gap tool
• Torque wrench for accurate tightening (optional)

To do it safely and avoid any damage, keep these tips in mind:

• Work on a cold engine to prevent burns and avoid damaging the threads
• Hand-thread the new plugs first to avoid cross-threading
• Check the spark plug gap before installing
• Don’t overtighten, as this can damage the engine

If your spark plugs are hard to reach or you’re unsure, it’s best to leave it to a professional mechanic.

Can I use any spark plug for my car?

No, you can’t use just any spark plug – your car needs the right type to run properly. Spark plugs must match your engine’s specific requirements, including size, heat range, and gap. To get it right, always check your owner’s manual or use a trusted parts guide to find the correct spark plugs for your car.

Can using an old spark plug damage my car?

Yes, using old or worn spark plugs can damage your car if left unchecked. Leaving them too long isn’t just bad for performance – it can lead to much more expensive repairs over time.

In the worst-case scenario, you could even face a full engine replacement. Depending on the type of engine and vehicle, this can cost anywhere from £1,500 to £8,000+, according to engine rebuilding service Allied Engines.

Car change? Carwow!

Looking for a new set of wheels? With Carwow you can sell your car quickly and for a fair price – as well as find great offers on your next one. Whether you’re looking to buy a car brand new, are after something used or you want to explore car leasing options, Carwow is your one stop shop for new car deals.

Click here to follow us on WhatsApp, where you can keep up-to-date with all the latest news, reviews, advice guides and videos.