How Often To Change Spark Plugs (2020 Guide)

Ever wonder how often to change spark plugs in your car? Don't worry, we've got the answer!

In this guide, you'll learn:

  • Signs of faulty spark plugs 
  • What bad spark plugs look like
  • How to change spark plugs

And more!

Time to Change Those Spark Plugs? How Often To Change Spark Plugs.

The ignition system is responsible for delivering properly timed spark to each cylinder to facilitate combustion.

One of the most vital ignition components is your vehicle’s spark plugs, which must be replaced from time to time as a matter of maintenance, typically known as a tune-up. 

However, this naturally leads to the question of how often spark plugs are to be changed.

So, to learn more about how to take care of your spark plugs for the long-haul, read our helpful guide below to become a Pro!

Timing Is Everything

The simple answer to the question of how often to change spark plugs, is at the factory recommended service interval.

The exact recommended mileage between such service can differ to an extent from one manufacturer to the next, and varies among different types of spark plugs.

However, the most common of these mileage intervals are typically in the ballpark of every 30,000 miles.

For exact specifications regarding replacement intervals, always consult your vehicle’s owner’s manual, contact an appropriate, dealership-specific service center, or visit a reputable automotive dealer website.

Although intervals of this nature typically dictate the time at which spark plugs are to be replaced, this is simply not the only time in which replacement becomes necessary.

At times, spark plug replacement becomes required when a mechanical issue with one or more plugs is detected. But, how is one to know when such an issue has come to pass? 

Did You Know: How spark plugs work

Signs Of A Faulty Spark Plug

 When a spark plug does not fire, as it should, several effects to your vehicle’s performance can become noticeable, and new plugs should be installed.

The severity of these issues often comes down to the exact type of spark plug failure that has taken place, and what the root cause of such a failure was. 

The following are common signs of a failing spark plug, which in any event would require further diagnoses and/or plug replacement.

A Miss Or Rough Idling

When a spark plug fails, the particular cylinder that corresponds to that plug does not combust as it should, leading to a misfire.

This leads to an unevenness that can be felt at idle, as well as under both cruising and accelerating conditions, in most cases.

An Illuminated Check Engine Light

A failed spark plug is often accompanied by an illuminated check engine light. This is due to the ability of your vehicle’s computer to detect and track engine misfire events.

The engine’s management computer notates the misfire, and a check engine light is triggered as a way to make you aware of the issue, as a poorly running engine can lead to both drive-ability issues and an increase in harmful emissions.

Decreasing Engine Performance

When an engine is forced to run without all of its cylinders contributing evenly, performance suffers. A once strong running engine can suddenly fall prey to poor acceleration, and less than overwhelming throttle responsiveness.

Decreasing Gas Mileage

When you experience inadequate spark on any one of your engine’s combustion chambers, fuel cannot be burnt efficiently.

This, in turn, leads to high fuel consumption and poor overall fuel economy. In short order, trips to the pump can increase in frequency.

Whenever any of the above mentioned symptoms become evident, it is often necessary to rule out other issues, such as a failing ignition coil, as the root cause of what you are experiencing, before concluding that your spark plugs are the culprit.

You can also remove your spark plugs and inspect them for any signs of carbon fouling, fuel saturation, or out-of-specification gap. This article has more about signs of bad spark plugs.

Read More >> What Does a Bad Spark Plug Look Like?

An Old Spark Plug That You Should Change

What Do Bad Spark Plugs Look Like?

If there is any indication that your vehicle might have one or more inoperable spark plugs, a few minutes of work under the hood can be all that is needed to confirm or deny your suspicions. You can assess the health of your spark plugs by simply removing them from your engine, and looking for any signs of discoloration, fouling, or dampness. 

For more on the conditions of spark plugs, follow this link. The following are some of the most common spark plug irregularities.

Carbon Fouling

Carbon fouling is characterized by black, soot-like deposits in or around the spark plug’s electrode or insulator. This is often caused by an overly rich air/fuel mixture, long periods of vehicle idle time, and air filter restrictions. In any event, spark plug replacement is necessary under these conditions. 

Electrode Wear

When a spark plug is removed from its corresponding cylinder; its gap should be checked. If this gap is found to be outside the factory recommended specification, replacement is advised, as an extended service life has led to excessive wear.

Wet Condition

 If you remove your spark plugs, only to find their tips saturated in moisture, you are likely staring at the result of a flooding condition. The moisture that can be seen is fuel, and until it dries or is cleaned from the plug, you will experience less than adequate operation.

Oil Fouling

Plugs that are fouled with oil indicate larger issues than just a simple loss of spark. The presence of oil signifies the possibility of damaged/worn piston rings or worn valve guides. Plugs of this nature should be discarded, and the root cause of this oil saturation must be evaluated.

Read More >> How to Clean a Spark Plug

Changing Spark Plugs

When you have confirmed that your vehicle’s spark plugs need to be changed, as a regular item of maintenance, or to remedy a performance concern, it will be time to tackle the task at hand.

The difficulty of spark plug replacement can differ substantially between vehicles, although the plugs used in the majority of makes and models can be replaced in a relatively straightforward and trouble-free fashion. This article talks more about changing spark plugs.

 Changing spark plugs, in general, is no more difficult than removing the spark plug wire or coil-pack from the plug itself, and unthreading it out of your engine’s cylinder head. Often the most difficult part of the job is gaining access to the plugs’ locations.

This can be made much easier with the assistance of an extension and swivel, in conjunction with a ratchet and spark plug socket. In most cases, vehicle-specific service literature, including torque specifications, are available to assist you in completing this task.

Read More >> How to Check a Spark Plug

How Often Is Often Enough?

Deciding when to change your spark plugs does not have to remain a mystery.

As a general rule, there are only two times when installing new spark plugs would be necessary; when your vehicle has reached the factory specified service interval, or when your vehicle’s engine Is misfiring or idling poorly, and plug failure is suspected. 

Between your vehicle's maintenance manual and a keen attentiveness as to the state of your engine’s performance, you will never again be left to wonder if it is time to change your car’s spark plugs.

Read More >> How to Gap a Spark Plug

About Your Mechanic

About Josh Boyd

I’ve been an ASE Certified automotive/heavy equipment technician since 2010. I began my career performing basic automotive maintenance at a service center before working as a Toyota technician at my local dealership.

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