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How Often Should You Change Spark Plugs?

Spark plugs. Changing spark plugs is a part of completing preventive maintenance on a car. Here's how often spark plugs should be replaced.

How often should you change spark plugs? How long does it take to replace spark plugs? These ignition parts play a crucial role in the operation of a car’s internal combustion engine, influencing everything from acceleration to gas mileage. They need proper care if you want your vehicle’s engine to perform at its best. Below, we’ll take a look at how often spark plugs need to be changed, and we’ll talk about what can happen if these parts aren’t replaced in a timely manner. We’ll also provide a step-by-step guide for changing a typical car’s spark plugs.

Timely Replacement Is KeySpark plugs

You can answer the question, “How often should you change spark plugs?” by taking a look at your car’s owner’s manual. The manual will list when to change spark plugs at a recommended replacement interval. Usually, replacement is required every 30,000 miles but not always. Some modern vehicles suggest changing spark plugs every 100,000 miles thanks to advances in materials and ignition design.

You can also periodically inspect your spark plugs for fouling and wear every 30,000 miles. This gives you a good look at how the combustion process is performing as the plug can have tell-tale signs on it. Black soot or burned spots on the plugs can signal something is wrong and should be further investigated. The spark plug gap should also be checked and adjusted if necessary. Inspecting the spark plugs also helps keep them from becoming stuck in the cylinder head when it is time to change them later.

If you don’t replace your car’s spark plugs in a timely way, you could be setting yourself up for engine problems such as misfiring, lack of proper acceleration and uneven idling. Failure to replace old spark plugs could also cause your car to consume excessive amounts of fuel.

How to Replace Your Car’s Spark Plugs

How long does it take to change spark plugs? Replacing spark plugs will take roughly an hour if your vehicle has a four-cylinder engine. With a V6 or V8, it could take two to three hours. The cost to replace spark plugs will also vary by vehicle, as some spark plugs designs are more expensive but are designed to last longer. Always use the exact spark plug type specified for your vehicle or else other issues could arise.

It’s a fairly straightforward task with four-cylinder engines, and if you have experience working under the hood, you should be able to handle the project yourself. However, the job gets more complicated with a V6 or V8. If your vehicle has one of these engines, you may want to turn the job over to a mechanic.

To handle this project, you’ll need:

Now that you have the tools you need, you’re ready to get started:

  1. Clean the area around the spark plug using the shop vacuum, making sure to wear goggles as eye protection. Do NOT use compressed air as it may blow dirt and grit back in your direction. Removing dirt from this area will help prevent debris from entering the engine’s combustion chamber once the plug is unscrewed.
  2. Remove the spark plug wire or coil pack from the first spark plug, using a spark plug wire puller. Wait until each plug has been removed and replaced before moving on to the next wire. This will help make sure you attach the right wire to each plug.
  3. Spray a small amount of lubricant at the base of the spark plug and wait five minutes for it to soak in. This will help break the spark plug loose if it has been in place for a long time.
  4. Use a swivel-head spark plug socket to remove the spark plug. Turn the plug counter-clockwise to unscrew it. If the spark plug does not loosen with medium effort, apply spray lubricant at the base of the plug again and wait 30 minutes to soak in further.
  5. In your car’s owner’s manual, locate the section that tells you how much of a gap there should be between each spark plug’s two electrodes. It may also be printed on a sticker under the hood.
  6. Check the spark plug gap on the new plug before installation to make sure it aligns with the measurement given in the car’s owner’s manual. Utilize a spark plug gauge to measure the gap between the plug’s two electrodes.
  7. If the gap needs to be adjusted, employ the spark plug gauge to handle the task. Use the gauge to bend the curved electrode until the correct gap is attained.
  8. Install the new spark plug using a torque wrench. Be careful not to over-tighten it. Pro tip: use a piece of rubber hose to slipped over the spark plug terminal to install the spark plug. The rubber hose is flexible and can hold the plug where fingers can’t reach, while also preventing cross-threading by limiting torque.
  9. Reinstall the spark plug wire or coil pack.

Regularly replacing your car’s spark plugs can help keep your vehicle’s engine in good health. This task is one you may be able to handle yourself. Just remember to change one plug at a time to help keep things simple.

Check out all the electrical & ignition system products available on NAPAOnline or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on how often should you change spark plugs and spark plug replacement cost, chat with a knowledgeable expert at your local NAPA Auto Parts store.

Photo courtesy of Wikimedia Commons.

Warren Clarke View All

I'm a writer and editor who's a regular contributor with the New York Daily News and Carfax, and my content has appeared in over 20 publications. I've written content that covers industries such as automotive, medical, insurance, healthcare, real estate, plumbing, pest control, dental and hospitality.

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