How long do spark plugs last?
If you’re wondering about this, you are probably dealing with issues like slow starts and rough idling, or simply trying to keep up with regular maintenance.
Either way, it’s good to know what to expect.
In this guide, we’ll explain how spark plugs work, why they wear out, and when to replace them. We’ll also share some smart ways to make them last longer so your drives stay smooth and stress-free.
This Article Contains:
- What Does a Spark Plug Do?
- How Long Do Spark Plugs Last?
- What Causes Spark Plug Damage?
- 5 Warning Signs of a Failing Spark Plug
- What Happens if You Don’t Change Your Spark Plugs?
- How Much Does It Cost to Replace Spark Plugs?
- 3 FAQs About Spark Plugs
What Does a Spark Plug Do?
A spark plug is a small yet essential part of your engine that plays a key role in starting and powering it.
It pulls electrical current from the ignition system and fires a spark across a small gap at its tip. This spark lights up the air-fuel mixture inside the engine cylinder, setting off a mini-explosion that pushes the piston down. This movement powers the engine and gets the wheels rolling.
Now that you know what spark plugs do, let’s look at their expected lifespan.
How Long Do Spark Plugs Last?
The average spark plug lifespan depends on its brand, model, and type.
Here are the estimates of different spark plug types:
- Copper spark plug: 10,000 – 20,000 miles
- Silver spark plug (used for older vehicles): 20,000 miles
- Budget iridium spark plug and platinum spark plug: 60,000 miles
- Premium iridium spark plug and double platinum spark plug: 100,000 miles
Wondering what wears out a spark plug?
Let’s take a closer look.
What Causes Spark Plug Damage?
Your spark plugs may fail due to:
- Natural wear and tear: Spark plugs have a protective anti-corrosion coating that gradually wears off with time and use.
- Carbon and debris buildup: When your engine isn’t burning fuel properly, combustion byproducts like carbon deposits and debris can start to coat the spark plugs. This buildup can block the spark and reduce overall fuel efficiency.
- Improper spark plug gap: The gap between the spark plug’s center and side electrodes must be precise. If it’s too wide or too narrow, it can lead to poor combustion, misfires, and added strain on the ignition system, resulting in a failing spark plug.
- Overheating: Excessive heat from the combustion chamber or a malfunctioning cooling system can cause spark plug tips to overheat. Repeated overheating can lead to premature spark plug wear.
- Oil leaks: If engine oil leaks into the combustion chamber, it can coat the plugs, reducing their ability to generate a clean spark. This often results in misfires and poor engine performance.
- A bad fuel filter: A clogged or failing fuel filter allows dirt and grime into the fuel system. These contaminants can accumulate on the spark plugs, damaging the insulators and causing misfires or erratic engine timing.
- Lack of regular maintenance: Skipping routine engine tune-ups or ignoring the manufacturer-recommended replacement interval can lead to premature spark plug wear.
If any of the above conditions damage your spark plugs, there will be obvious symptoms. Keep reading to know how to spot these.
5 Warning Signs of a Failing Spark Plug
If your spark plugs are damaged, you may notice:
- An illuminated check engine light: A faulty spark plug can cause misfires and trigger the check engine light to turn on.
- Hard starts: If your car struggles to start, the culprit could be a worn plug not producing enough spark to ignite the engine.
- Rough idling: If your engine shakes or makes knocking and rattling sounds while idling, it could be misfiring due to a worn spark plug.
- Sluggish acceleration: When spark plugs get dirty or worn, they can’t ignite the fuel properly, leading to slow or jerky acceleration. In some cases, your engine might also stall or sputter.
- Poor fuel efficiency: A bad spark plug can force your engine to work harder, leading to lower mileage and fuel economy. If you’re filling up more often than usual, it might be time to check the plugs.
So, is it okay to drive around without addressing these issues?
Read on to find out.
What Happens if You Don’t Change Your Spark Plugs?
As spark plugs age, the gap between their electrodes gradually widens due to wear and carbon buildup. This makes it harder for the ignition coil to generate the voltage needed to create a spark, increasing the risk of engine misfires. In severe cases, your engine may lose power, struggle to start, or not start at all.
Over time, the spark plug wires (if your vehicle has them) can also become brittle, weakening the connection between the ignition coil and the spark plug. This leads to inconsistent sparks and incomplete combustion, which can send unburned fuel into the exhaust system and hurt your fuel economy.
The result?
Overheating and potential damage to the catalytic converter — an expensive fix you’d rather avoid. That’s why it’s important to replace a worn spark plug at the recommended interval.
Next, we’ll explore the expenses involved in a spark plug replacement.
How Much Does It Cost to Replace Spark Plugs?
Spark plug replacement costs depend on the number of cylinders in your engine. Each engine cylinder has one spark plug, so the more cylinders, the higher the expense.
The average cost for replacing a spark plug set is between $50 and $750. This includes the labor cost of $40 to $350 and the price of spark plugs.
However, the cost also depends on the material of the spark plugs. High-end spark plugs (such as iridium plugs) are more expensive than conventional spark plugs (copper plugs).
Here’s a breakdown of cost estimates for different types:
- Copper spark plugs (or standard spark plugs): $2 to $10 per piece
- Silver spark plugs: $5 per piece
- Platinum spark plugs: $10 per piece
- Double platinum spark plugs: $20 per piece
- Iridium spark plugs: $20 to $100 per piece
NOTE: Most automotive mechanics recommend replacing all the spark plugs together for optimal performance. That’s because if one’s worn out, the rest are likely close behind.
Got more questions?
Let’s explore a few commonly asked questions about spark plugs to clarify things further.
3 FAQs About Spark Plugs
Here are a few additional spark plug queries and their answers:
1. How Do You Choose the Right Spark Plug for Your Vehicle?
Follow these tips to pick a new spark plug set that suits your car:
- Match the size and fit: The spark plug must be the correct size for your engine, including the thread diameter, length, and reach. If it doesn’t match your engine’s cylinder bore, it can lead to poor combustion or even serious engine damage.
- Check the spark plug gap: The spark gap, or the distance between the center and ground electrodes, must align with your vehicle manufacturer’s specifications. A gap that’s too wide or narrow can cause misfires, rough idling, and lead to poor fuel efficiency.
- Choose the right material: Spark plugs come in different materials, each suited for specific needs:
- Copper spark plugs or conventional spark plugs are suitable for older or standard engines.
- Platinum plugs and iridium spark plugs are ideal for modern engines and high-performance vehicles due to their longevity and ignition efficiency.
- Read the vehicle manual: Always check the manufacturer’s recommendations to ensure the compatibility of a spark plug. If unsure, schedule service with an experienced mechanic to guide you.
2. How Can You Check Spark Plugs for Damage?
If you suspect worn-out spark plugs, it’s best to have a professional take a look. They can quickly spot signs of wear, overheating, or internal engine issues that might not be obvious to an untrained eye.
Here’s how a mechanic will proceed. They’ll:
- Let the engine cool down completely before proceeding.
- Use a spark plug socket to carefully remove each plug from the cylinder head of the internal combustion engine. For standard or copper plugs, a basic spark plug socket will do. However, for iridium or platinum plugs, a swivel spark plug socket might be needed to reach tighter spaces.
- Examine both the center and ground spark plug electrodes. Look for black soot (carbon fouling), oil residue, or worn edges. These are signs of an incorrect air-fuel mixture or incomplete combustion.
- Use a gap gauge to ensure the spacing between the spark plug electrodes is correct. An incorrect gap can lead to misfires and reduced engine performance.
- Look for cracks, brittleness, or signs of corrosion in the spark plug wires or ignition coil connectors.
If a plug shows signs of wear, they’ll replace it with a new spark plug.
3. How Do You Make Your Spark Plugs Last Longer?
Here are a few things you can do to maximize your spark plug lifespan:
- Regularly inspect the electrode ends to ensure that they’re clean. Check to see that the center electrode and ground electrode do not have any rust buildup.
- Ensure that your spark plug wire boots and porcelain insulators are lightly coated with dielectric grease. This prevents problems like premature corrosion and carbon deposits from penetrating the insulator.
- Maintain the spark plug gap. If the electrodes are too close, it may damage the old spark plug and cause an engine misfire. And if it’s too far, the plug may not generate an electric spark at all. It’s best to refer to your owner’s manual for the appropriate gap.
- Regularly clean the spark plug seating area on the cylinder head. Accumulation of dust and dirt can sometimes misalign the spark plugs.
- Most importantly, ensure that you have your mechanic check your spark plugs at the recommended miles for optimal performance.
Get Your Spark Plugs Examined and Replaced by Pros
One bad spark plug can sabotage your engine’s performance — or stop your car from starting altogether. Don’t wait for it to become a bigger, more expensive problem.
The good news is you can skip the hassle of going to a repair shop.
With AutoNation Mobile Service, our expert technicians come to your driveway to replace worn-out spark plugs — seven days a week, with upfront pricing. And because peace of mind matters, we back every repair with a 12-month, 12,000-mile warranty.
Book your service today to spark some life back into your engine.