DIY: How to Replace Spark Plugs on a Subaru Impreza for Improved Fuel Efficiency

Regular car maintenance is crucial for keeping your vehicle running smoothly and efficiently. One of the essential maintenance tasks that every car owner should learn is how to replace the spark plugs. In this article, we will guide you through the process of replacing spark plugs on a Subaru Impreza, one of the most popular and reliable vehicles on the market.

Why Replace Spark Plugs?

Spark plugs are responsible for igniting the fuel and air mixture inside the engine, which creates the power that makes your car move. Over time, spark plugs wear out, get dirty, and become less effective. This can result in reduced performance, decreased fuel efficiency, and even engine damage if left untreated.

Replacing your spark plugs on time will not only improve your car’s performance but also help you save money on gas in the long run. That’s why it’s essential to understand when your spark plugs need to be replaced and how to do it yourself.

When to Replace Spark Plugs on a Subaru Impreza

The replacement interval for spark plugs varies depending on the make and model of your vehicle. In general, the OEM (original equipment manufacturer) recommendation for a Subaru Impreza is every 60,000 miles or 5 years, whichever comes first. However, if you notice any of the following symptoms, you should consider replacing your spark plugs sooner:

  • Reduced engine power and acceleration
  • Poor fuel economy
  • Rough idle or misfires
  • Check Engine light on
  • Difficulty starting the engine
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Tools and Materials You Need

Before you start replacing your spark plugs, you need to gather the necessary tools and materials. Here’s what you’ll need:

  • New spark plugs (make sure you get the correct type for your Subaru Impreza. Check the owner’s manual or consult with the dealership if you’re unsure.)
  • Spark plug socket or wrench (size may vary depending on the model year, so check your owner’s manual)
  • Extension bar
  • Ratchet
  • Spark plug gap gauge
  • Dielectric grease
  • Torque wrench (optional but recommended)

How to Replace Spark Plugs on a Subaru Impreza

Now that you have all the tools and materials, let’s get started. Follow these steps to replace your spark plugs on a Subaru Impreza:

  1. Park your car on a flat and level surface, and let the engine cool down completely. Working on a hot engine can be dangerous and cause burns.

  2. Open the hood and locate the spark plug wires on top of the engine. Depending on the model year, your Subaru Impreza may have either coil-on-plug or spark plug wires. If you have spark plug wires, gently remove them one by one from the spark plugs using a twisting motion. If you have coil-on-plug, unscrew the bolts holding them in place and remove the coils.

  3. Use the spark plug socket, extension bar, and ratchet to remove the old spark plugs from the engine block. Turn them counterclockwise to loosen and remove them carefully. Take note of the condition of the old spark plugs, which can give you clues about the health of your engine.

  4. Use the spark plug gap gauge to measure the gap between the electrodes on the new spark plugs. Adjust the gap if necessary (refer to the owner’s manual for the correct gap specification).

  5. Apply a small amount of dielectric grease to the threads of the new spark plugs and insert them into the engine block by hand. Tighten them gently with the spark plug socket and ratchet until snug.

  6. If you’re using a torque wrench, refer to the owner’s manual for the correct torque specification and tighten the spark plugs to the recommended torque. If you’re not using a torque wrench, tighten the spark plugs to about 1/4 turn past finger tight.

  7. Reinstall the spark plug wires or coil-on-plug, making sure they click or bolt into place. Double-check that everything is secure, and close the hood.

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Congratulations, you have successfully replaced the spark plugs on your Subaru Impreza! Start the engine and check for any abnormal noises, vibrations, or warning lights. If everything looks and sounds normal, take your car for a test drive to feel the improved performance and efficiency.

Safety Precautions

Replacing spark plugs on a Subaru Impreza is a relatively simple task, but it involves working around the engine and electrical components. To avoid accidents or damage to your vehicle, follow these safety precautions:

  • Always work on a cool engine to prevent burns.
  • Use proper tools and wear protective gear, such as gloves and goggles.
  • Do not touch, disassemble, or remove any electrical components unless you know what you’re doing. Disconnect the battery if necessary.
  • Do not overtighten or undertighten the spark plugs, as this can cause damage to the engine block or the threads.
  • Dispose of the old spark plugs and other waste materials properly.


Q: Can I replace spark plugs myself if I have never done it before?

A: Yes, you can. Replacing spark plugs is a simple task that doesn’t require extensive knowledge or experience. Just follow the instructions in this article and use the right tools and materials.

Q: How often do spark plugs need to be replaced on a Subaru Impreza?

A: The OEM recommendation is every 60,000 miles or 5 years, but it’s best to check your owner’s manual for the specific interval for your model year. Some models may have a different recommendation.

Q: Can I use any spark plugs for my Subaru Impreza?

A: No, you should use only the recommended spark plugs for your vehicle to ensure proper performance and compatibility. Check your owner’s manual or consult with the dealership for the correct type.

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Q: What are the benefits of replacing spark plugs?

A: Replacing spark plugs on time can improve your car’s performance, increase fuel efficiency, and prevent engine damage. It can also save you money on gas and repairs in the long run.

Final Words

Replacing spark plugs on a Subaru Impreza is a practical and rewarding DIY task that every car owner should learn. By following the steps and safety precautions outlined in this article, you can improve your car’s performance and save money on gas. Remember to always use the recommended tools and materials, and don’t hesitate to consult with a professional if you have any doubts or concerns.

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Alton Brobst

As a longtime Subaru enthusiast, Alton brings a wealth of knowledge and experience to our blog. From his early days of tinkering with engines to his current role as a certified Subaru technician, Alton has seen it all when it comes to Subarus. When he's not working on cars, he enjoys hiking and exploring the great outdoors.

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