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Are Spark Plugs Universal? Interchangeable?

Close-up of a spark plug on a black background.

As far as I know, spark plugs are only universal or interchangeable if they’re an exact match of what’s in your car. This doesn’t mean they have to be the same brand, but they will need to fit in the spot where you removed them. 

What happens if you use the wrong spark plugs? 

If the spark plug threads are too large, they won’t fit in the sockets anyway, so that won’t put you in much danger. The worst problem you’d have is they would fall out of their socket when driving if the threads don’t match. 

You could end up stalled somewhere. If the place where your vehicle quits on you is at an intersection or a highway exit ramp, this is not much fun. 

What are signs of using the wrong spark plugs? 

Old spark plug in the mechanic's hand, with a car's blurry engine in the background.

“Good spark plugs will burn fuel efficiently, while bad or failing spark plugs can cause the motor not to start at all,” says Your Mechanic. 

That’s what typically happens when you have bad spark plugs. However, I think that also occurs if you use the wrong ones

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You also can experience slow acceleration rates, engine misfiring or “popping” and car shaking. If your car still does start, you will probably notice a “hard” start. 

You may even have to turn the key on and off a few times and risk flooding your fuel line when pressing the gas pedal. That’s because you’re not getting the “spark” you need to fire your engine (ignite it to start). 

Do wrong spark plugs cause engine damage?

“Do wrong spark plugs damage the car engine? The answer is not as straightforward as it may seem,” says Jack Y. M of Car Topics. 

Jack continues explaining that an inductive spark plug that has a resistance-type ignition system could cause misfiring. The car also starts to perform poorly, and the sudden loss of power that could occur may cause it to stall. 

So many variables occur as to what a wrong spark plug would do. It may not cause any damage at all in some cases though. I would say you’re lucky if you run your vehicle unaffected with the wrong spark plugs. 

Why do cars need spark plugs? 

A picture of a spark plug being installed correctly in an automobile.

The spark plug triggers the combustion (“explosion”) that starts your engine. It’s almost like lighting a match, which supplies the heat you need to start a gas stove. You also notice a similar reaction when pulling a chainsaw or lawn mower cord. 

How do spark plugs work? 

Friction is caused when you turn your ignition key or press a button. Only it’s an electrical charge from the battery rather than a fire lit after striking a match that activates the ignition coil. This power is sent to the spark plugs, which ignite the fuel, turning the electricity into mechanical power. 

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How do you find the right spark plugs for your car?

Spark plugs on black background.

Every car still has an owner’s manual. If you don’t have yours, you can find a copy of it through your dealer or the manufacturer ready for download. Check it for information about how to find the right spark plugs. 

Otherwise, you’ll have to perform a parts search based on your make and model of vehicle. Nowadays, you can enter this car part data into an online database. However, some stores still have paper directories in them that list all the parts according to your specific vehicle. 

Spark plugs also need to be matched with your engine’s ignition system. Some auto parts stores and service centers may supply this information for you if you can’t find your manual. 

Do the spark plugs for a car need to be a certain brand? 

They don’t necessarily need to be the same brand as the ones already installed in your car. However, it’s best to replace the ones in your vehicle with the same type. 

For instance, some cars run better on spark plugs made of iridium materials. If so, Champion Auto Parts suggests that you not downgrade to copper or platinum plugs. 

If you normally have your car tuned up by a mechanic your dealer recommends, that’s the most assured way to find the right replacement plugs. However, that can also cost you more too. 

It’s possible to find OEM (original equipment manufacturer) parts for your make and model of vehicle for less expensive rates than at a dealership mechanic shop. 

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How do you know if you have the right spark plugs?

Isolated, new spark plug on a white background.

Dummies author Deanna Sclar of “How to Buy the Right Spark Plugs” provides a thorough guide. Sclar says not to just ask a salesperson what plugs to buy. This increases the chance that you will end up with the wrong ones

I am shocked to think that someone who works in an auto parts store may not know enough about the parts they sell. Still, I do see the point of finding out for yourself what the right ones are. 

Finding the right replacement spark plugs calls for as much information as you have. Besides knowing the make, model, and year of your car, you also should know this:

  • Type of engine
  • How many cylinders 
  • Automatic or manual transmission
  • Engine displacement room (space in each cylinder)

I suggest a good mechanic if, after reading about how to buy the right spark plugs, it causes you to feel overwhelmed. It’s more involved than you might think, so be careful when deciding which plugs to install.

Related: How Does a Spark Plug Work? | How Can You Tell When a Spark Plug is Bad (Needs Replacing)?