Do diesel cars have spark plugs?

Past knowing whether we’re driving a diesel or a petrol car, many of us are baffled by the list of things that are supposedly under the bonnet. One of these things is a spark plug, those seemingly magical little things that are apparently crucial to making our cars run.

But what are spark plugs? Why do they matter? Do you even have them in your car? Don’t panic, we’re not asking you. We’ve actually written this blog to answer those questions for you. Isn’t that lucky?

What are spark plugs?

Spark plugs are little engine components that play a pretty important part in making sure a petrol engine starts properly and runs smoothly. Spark plugs sit in the engine cylinders and connect the engine to the ignition. When electricity reaches the spark plug, they create a spark inside the cylinder, igniting the fuel and starting the combustion process.

Do diesel cars have spark plugs?

Spark plugs are only ever present in petrol engines, so diesel cars do not have spark plugs. Diesel engines use something called a glow plug instead. This is because of the way the combustion system in a diesel engine works.

Diesel engines ignite the fuel using compression, whereas petrol engines use the spark plugs. Glow plugs heat up the cylinders in a diesel engine before the fuel is compressed, so that the energy from the fuel goes into making it move rather than just heating up the cylinders.

So, diesel cars don’t have spark plugs, but petrol cars do.

If you’d like to learn a bit more about diesel cars, you can check out our blog ‘Should I buy a diesel car?’

How many spark plugs are in my car?

How many spark plugs your car might have will vary. This is because the vast majority of cars will have one spark plug per cylinder, and the number of cylinders a car has varies depending on its model and engine. Some cars have HEMI engines (big engines usually found in muscle cars) which use two spark plugs per cylinder, but most cars just have one. If you’re not sure about how many cylinders your car has, you can look up your car make and model to find out, or ask a mechanic.

How do I clean my spark plugs?

Spark plugs can build up gunk and grease over time, as with most car parts. Most spark plugs can self-clean to a certain extent, but this needs the engine to get up to temperature to work properly. If you’re regularly taking short journeys or spending a lot of time in stop-start traffic, you might be getting build-up on your spark plugs. If you’re experiencing misfires or having trouble starting your engine, it’s possible your spark plugs could do with a clean.

If your car is struggling to start and you’re worried you might have used the wrong fuel, you can check out our blog ‘Can you put diesel in a petrol car?’

If you think it’s time to clean your spark plugs, you have a couple of options. The first option is to take them to a mechanic to take care of the job for you. This might seem like overkill but the issue is that not all spark plugs are easily accessible, so you may have some issue actually getting to them if you’re not used to navigating an engine.

If you’re a confident home mechanic, you could try to clean your spark plugs yourself. If this is the case, here’s what you can do to give them a clean:

• Safely remove the spark plug from the cylinder
• Use a carb spray cleaner to remove gunk, grease, and oil from the electrode tip
• Remove excess grease with a soft rag/cloth or additional spray cleaning
• For a deep clean, you can remove ingrained dirt using a wire brush, but be careful not to damage the spark plug electrodes
• Re-gap the spark plug, replace the washer or gasket and tighten to recommended torque (check your car manual for the re-gap distance and torque)

If you’re still having issues, it might be time to have your spark plugs tested and possibly replaced.

How often do I need to change my spark plugs?

Spark plugs do tend to wear out over time, and how long they last  tends to depend on their type and the car they’re in. Spark plugs can come in copper, iridium, or platinum, all of which have varying levels of hardiness. The type you have in your car will depend on your manufacturer's recommendation most of the time, with platinum tending to be the longest lasting. Spark plugs can last for anywhere between 10,000 and 30,000 miles, but most mechanics would recommend getting them changed as part of a full service, well before you start experiencing any engine issues. If you’re having any problems with misfiring or having trouble starting your car, it might be time to have them changed.

Can I change my spark plugs myself?

In theory, changing spark plugs is a pretty simple procedure, and should be easily done. However, changing your own spark plugs can pose the same problems as cleaning them. Spark plugs can be hard to reach, and any mistakes have the potential to cause problems with your engine. If you are a confident home mechanic, there are plenty of instructional pages out there to help you change them, and your car’s manual will likely have a simple guide as well. If you’re not so confident, you can always take your car to a professional mechanic.

If you’re curious about the inner workings of your car, you can check out our blog ‘Is my car compatible with E10 fuel?’

How much does it cost to change spark plugs?

The cost of changing your spark plugs will vary on how many spark plugs are in your engine, and how your engine is built. This is because more complicated engines with more spark plugs tend to take more time to take apart and replace. It’s a good idea to get all of your spark plugs replaced at the same time to avoid any timing issues in the engine.

All together, the cost of a spark plug change can cost anywhere from £40 to £350, so it can be worth doing some shopping around to find a good price. You can also ask to have your spark plugs changed as part of a full car service, which may help to bring the price down as it’ll  likely be incorporated  into the price of the service.

A few final tips…

So that’s the mystery of spark plugs unmasked. Here are a few things to remember:

• Diesel cars do not have spark plugs, but petrol cars do
• The number of spark plugs your car has will usually depend on how many cylinders your engine has
• You might want to clean or replace your spark plugs if your engine is misfiring or struggling to start
• It might be better to get your spark plugs cleaned or replaced by a mechanic rather than trying to do it yourself

Urban Jungle is not a financial advisor and information in this article should not be taken as advice or recommendation.