When To Change Spark Plugs – A Quick Guide

When Should You Change your Spark Plugs…

when to change spark plugsIf you own a vehicle chances are you’ve had to change your spark plugs once or twice.

However, if not, you might not be sure exactly when you should be changing them.

Read on to learn more about spark plugs, what they do, and how often they should be changed.

When To Change Spark Plugs

What Do Spark Plugs Do?

Spark plugs are an important part of your car’s efficiency. They emit a small spark of electricity that is needed to start your vehicle.

Without this small spark your car simply would not start.

The health of your vehicle’s spark plugs is directly linked to how well your engine performs.

For this reason, spark plugs that are weak or bad can lead to many problems such as misfires during acceleration or cold starting.

In addition, without healthy spark plugs your car will not be able to sustain maximum power resulting in an increase in fuel consumption.

You can find out more about how spark plugs work here.

How Often Should Spark Plugs be Replaced?

Fortunately, spark plugs don’t need to be changed that often.  They can last for several years and cover a lot of ground before they need to be changed.

A good rule of thumb is to replace your spark plugs at about every 25,000 to 35,000 miles. However, the life of a spark plug will depend on its type and condition.

For example, copper spark plugs don’t last as long as some of the more modern spark plugs which are made from more durable materials.

As spark plugs age they have endured thousands of miles of abuse. This is where the importance of the material that the spark plug is made from becomes relevant.

Obviously the more robust the material is, the longer the spark plug will last.

However, no matter what the spark plug is made of, it will have some wear and tear after going so many miles.

A buildup of deposit will form on spark plugs over time, which is one of the reasons that they don’t last forever. When your spark plugs develop this build up it can lead to a less reliable supply of energy to your vehicle.

In addition, as spark plugs age the gap becomes harder for it to jump. As the spark plug ignites it travels across a gap (you may have heard the phrase “spark plug gapping” before). This is so that it can provide the right amount of combustion when required.

Dirt, standard wear and tear, and high temperatures cause this gap to widen over time making it more tricky to “jump” and therefore less efficient.

Benefits of New Spark Plugs

The main benefit of replacing your spark plugs is simply knowing that your car is going to start without any difficulties.

In addition, replacing your spark plugs ensure the following:

  • Optimal combustion: spark plugs ensure that your combustion system functions properly, which can help improve many performance issues.
  • Fuel Economy: bad spark plugs can cause your vehicle to use more gas
  • Smooth starts: your car will start smoothly with new spark plugs
  • Reduces air pollution: always a good thing

How Difficult is it to Replace a Spark Plug?

Replacing the spark plugs in a vehicle in most cases can be very easy.  In others it can be a little more tricky.

All of the parts of the car have to be cold before spark plugs can be replaced. In addition, the amount of time it takes will depend greatly on the type of vehicle that you own.

There are some cars that require parts to be disassembled in order to access and replace spark plugs.

So be prepared to leave your car in the shop when you are having the spark plugs replaced.

when to change spark plugsYou can read our guide on how to change spark plugs here.

Signs your Spark Plugs Need Replacing

There are several signs which might indicate that your spark plugs need changing.

  • First, you may hear a knock or rattling sound. These sounds are often from the spark plug firing at the wrong time.
  • If you are having difficulty starting your vehicle it could be another sign that your spark plugs are bad.
  • In addition, overall vehicle performance may be poor.  Lethargic acceleration for example is a common sign of a bad spark plug.
  • If you notice that you are not getting as good of fuel mileage as you once were, this could also be a sign that you need new spark plugs put in. However, there are many different things that can cause poor fuel economy, including exhaust issues, so we’d recommend taking your car in to the shop for assessment if that is the case.

If you are experiencing any of these issues it’s a good idea to take your car in to have it checked out. If your vehicle is older and you have been driving it for a while, a routine maintenance session is always a good idea.

When to Change Spark Plugs – Conclusion

So there you have it!  In summary you should change your spark plugs every 35,000 miles or so, if you notice a drop off in performance, an increase in fuel consumption, problems starting your car, or when you hear unusual noises when your spark plugs misfire.

As ever, if you’re not confident diagnosing the problem take your car to a professional mechanic to do it for you.


Wondering when to change spark plugs?  Well, hopefully that helped.

Have you changed yours recently?  If so, what was the reason and how did you get on?

Let us know below…

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