How Often to Replace Spark Plugs: All You Need to Know

Is your car hesitating to start?
If it sputters at stoplights and feels sluggish when you accelerate, your spark plugs might be to blame.

But how often do you need to change them?
The answer depends on factors like your vehicle type, spark plug material, and driving conditions.

Since these essential components ignite the fuel in your engine, a timely replacement can prevent potential performance issues, reduced fuel efficiency, and unexpected breakdowns.

Let’s explore how often to replace spark plugs, the signs of damage, and the replacement process.

How Often to Replace Spark Plugs

Depending on the type used, spark plugs generally last around 20,000 to 125,000 miles. However, it’s best to replace them based on the recommended car maintenance schedule and manufacturer specifications.

Here’s the estimated lifespan based on the spark plug material:

Copper spark plugs have a solid core with a nickel alloy electrode and may need replacement every 20,000 miles.

Platinum spark plugs are more durable and can last up to 60,000 miles.

Iridium spark plugs can last up to 100,000 miles or more.

In addition to the type of spark plug, your driving habits and mileage can also affect its lifespan.

Now that we have covered the typical lifespan of spark plugs, let’s understand what causes them to wear out.

What Causes a Worn Spark Plug?

The following conditions can cause spark plug wear:

The continuous sparking process in a combustion engine gradually wears down the electrodes, reducing the plug’s effectiveness.

An overly rich fuel mixture (too much fuel and not enough air) can cause carbon buildup on spark plugs, insulating them and preventing proper firing.

Worn piston rings can leak oil into the engine’s combustion chamber, leading to oil-fouled spark plugs that struggle to ignite the fuel mixture.

Overheating, often caused by incorrect spark plug gaps or engine issues, accelerates electrode wear in the spark plugs.

Incorrect installation can cause premature spark plug wear.

These issues come with some unmistakable symptoms.
Read on to know more.

5 Signs Your Spark Plugs Are Faulty

If you notice the following symptoms, you may need a new spark plug:

Illuminated check engine light: A blinking engine light may signal a misfire caused by a faulty spark plug.

Hard starting: A failing spark plug can make starting your engine difficult, as a weak or inconsistent spark leads to poor combustion.

Rough idling and misfires: Worn-out spark plugs can lead to incomplete combustion, resulting in rough idling and poor engine performance.

Slow acceleration: Faulty spark plugs can weaken the spark needed for combustion, making your car lose power and feel sluggish.

Decreased fuel efficiency: If your gas mileage suddenly drops, faulty spark plugs may be forcing your engine to work harder, increasing fuel consumption and harmful emissions.

This leads us to the obvious question: Is it safe to drive when your car shows these symptoms?
Let’s find out.

Can You Drive with a Failing Spark Plug?

Technically you can drive with a faulty spark plug, but it isn’t a recommended practice.

Continuing to drive with a bad spark plug can cause engine issues such as misfires and stalling, which can be a safety hazard when driving.

Worn-out spark plugs can also lead to poor fuel economy and costly repairs. Persistent misfires can allow unburned fuel to enter the exhaust, potentially damaging the catalytic converter.

It’s best to replace damaged spark plugs as soon as you notice signs to prevent engine performance issues and costly repairs.

Got more doubts?
The next section covers some additional queries about spark plugs.

4 FAQs on Spark Plugs

Here are the answers to some common questions on spark plugs:

1. How Do Spark Plugs Work?

A spark plug creates a small electric spark to ignite the fuel-air mixture in a combustion engine. Each engine cylinder has one spark plug, which is essential for starting the engine.

The top of the spark plug connects to the ignition system, which delivers an electrical charge. Inside the cylinder, the spark plug features two electrodes, and the electricity jumps between them to create a spark.

This spark ignites the fuel-air mixture, triggering a controlled explosion that forces the piston down. The piston’s movement drives the crankshaft, converting the up-and-down motion into rotational energy — ultimately powering the vehicle’s wheels.

NOTE: Spark plug design plays a crucial role in its performance. A smaller electrode needs less voltage to create a spark, improving fuel economy and engine power. That’s why high-performance spark plugs are designed with finer electrodes and optimized gaps to enhance ignition efficiency.

2. How Do You Replace Spark Plugs?

Replacing a spark plug requires precision to ensure proper installation and prevent potential engine damage. That’s why it’s best to let a professional handle it.

Here’s how a mechanic will go about it:

Disconnect the negative battery cable to prevent electrical shocks.

Remove engine components obstructing access to the spark plugs, such as the spark plug wire and rubber boots (on older engines) or ignition coil packs (in modern cars).

Press down on the locking tab and unplug the electrical connector from the ignition coil.

Unscrew and remove the old plugs using a spark plug socket and ratchet, ensuring the threads remain undamaged.

Compare the new spark plug with the old one to ensure a proper match. Then, they’ll use a gap gauge to measure and adjust the electrode gap according to the vehicle’s specifications.

Screw in the new plug carefully by hand first, then use a spark plug socket and ratchet to tighten them. Finally, use a torque wrench to apply the manufacturer-specified torque for a secure fit.

Securely reattach the spark plug wire or ignition coil.

Reconnect the negative battery cable.

Start the engine and listen for any unusual noises to ensure smooth operation.

3. How Much Does Spark Plug Replacement Cost?

The average cost of replacing a spark plug set, including parts and labor, ranges from $50 to $500.

The replacement cost depends on the number of cylinders in your engine, with more cylinders leading to higher expenses.

NOTE: It’s best to replace all the spark plugs at once to ensure optimal performance.

4. What Preventative Maintenance Can Help Spark Plugs Last Longer?

Here are simple car tips to extend the life of your spark plugs:

Regularly inspect your spark plugs for wear or corrosion to catch issues early and prevent any engine problem.

Use high-quality fuel to reduce carbon buildup, keep your spark plugs clean, and protect your catalytic converter from damage.

Replace your spark plugs at regular intervals recommended by your vehicle’s manufacturer.

Select a plug that matches your engine’s requirements. Using the correct spark plug type can ensure optimal performance, fuel efficiency, and longevity.

TIP: Replacing spark plugs is a great opportunity to inspect other engine components, such as oxygen sensors and ignition coils. If your vehicle is also due for an oil change, it’s convenient to take care of both at the same time.

Get Hassle-Free Spark Plug Replacement with AutoNation Mobile Service

Spark plugs may be tiny engine components, but they play a significant role in your car’s performance. A bad spark plug can make your car struggle to accelerate or refuse to start altogether, leaving you stranded at the worst time. Ignoring replacement can also lead to decreased fuel efficiency and severe engine damage.

Fortunately, AutoNation Mobile Service can step in before things get worse.
Our skilled mobile mechanics can come to you to replace your spark plugs right from your driveway.

What’s more?
We are available seven days a week, offer upfront pricing, and back all our repairs with a 12-month, 12,000-mile warranty.

Book your service today for fast and reliable car repair.