How Long Do Spark Plugs Last and Why? Signs When to Replace Them

logo by Editorial Staff | Updated on July 1st, 2022

Every 30,000 miles, to be exact.

Spark PlugsDuration
Spark plugs need replacementEvery 30,000 miles
The life expectancy of spark plugs40,000 miles

Spark plugs are an essential component of a vehicle’s ignition system. The spark plug permits voltage to be transmitted from the battery to the combustion chamber through the wires.

Spark Plugs

A spark plug has an average lifetime of 2-3 years. This varies based on the kind of engine, the grade of fuel used, and how frequently the automobile is driven. Most automobiles’ spark plugs should be replaced every 30,000 miles, according to experts, to avoid significant engine damage.

If there are any problems with the automobile, it may be time to change the spark plugs.

What Is the Life Expectancy of Spark Plugs?

Engine problems occur when you least expect them. If a spark plug is not used, it can survive eternally in a suitable environment, but when it is time to replace the spark plug depends on its utilization. Proper service care will extend the life of the service. Spark plugs can last up to 30,000 miles throughout the life of an automobile.

A tune-up and routine examination of one’s automobile engine is necessary regularly. Replace plugs and wires at predetermined intervals to ensure maximum engine performance under different conditions.

However, the precise time to replace them is determined by how much use they receive, operating parameters such as air pressure and internal combustion temperature, and any other material deterioration that may cause wear-and-tear to occur more quickly than usual.

To avoid looking at the engine for indications from all those letters and numbers, many automobile manufacturers provide some standard maintenance intervals showing how to maintain the spark plug.

Spark plugs do not wear out on their own. It needs to be replaced only if the insulator is broken or burnt. As a result, if it’s not operating properly, but the plugs are new, start with the basics:

Gasoline quality: The wrong fuel type can block the small holes in a spark plug, preventing ignition from sparking and causing problems with the spark plugs.

Dirt will enter the lighter combustion chamber and electrical wires if the air filter is unclean.

Why are spark plugs so long-lasting?

Spark plugs normally last between 20,000 and 30,000 miles before needing to be changed. Therefore, a high-quality spark plug will last longer and be more dependable than a poorly built or low-quality competitor.

Spark plugs survive so long because they must provide a strong enough spark to jump the gap in the engine. This produces a lot of heat. They can accumulate carbon buildup over time, which is conductive and maintains a good connection that retains sparking at a high enough intensity for quick starts.

When there isn’t a lot of accumulation, this will continue to work. Still, it will accumulate additional accumulation over time, necessitating the spark plug replacement after 30,000 miles. Again, however, it depends on how aggressively the car is driven and wear and tear from other engine components (like brakes).

Among the several causes for this are:

  • The spark plugs feature a good heat and light conductor.
  • Extra material on each side guards against external factors such as moisture and dust, which can cause contamination and damage.
  • The plug converts the energy of the hot gas into an electric arc, which leaps some volt potential over a short gap to produce a brilliant spark.
  • The robust base insulator is broken before installation, allowing for deep end gaps and reduced carbon tracking throughout the length of the plug.

Overall, one deciding aspect of performance is how neatly and swiftly an engine’s internals can evacuate burnt fuel, trapped carbon deposits, and muck produced by combustion.

What exactly are spark plugs?

Spark plugs function similarly to small lightning bolts, providing the energy required to ignite the fuel/air combination in an engine’s combustion chamber. As a result, they play an important role in allowing the engine to start and function.

One spark plug is required for each cylinder of the engine. As a result, each spark plug requires a wire to link it to the coil’s distributor. Spark plugs appear to be simple devices, and in principle, they are. They do, however, need exact timing to function properly.

The bulb-like tip on one end connects to the wire head, which generates the high voltage required to transfer the energy that ignites the engine. A ceramic insulator is essential for safety since the charge can range from 40,000 to 100,000 volts. The alternator generates energy, which flows via the coil, distributor, and the core of the spark plug to the other end with the hook-like look.

The electrode is located on the outer core tab. The spark that ignites the fuel/air combination in the cylinder is formed in the gap between the hook and the charged electrode.

How do spark plugs function?

In the combustion chamber, the initial spark ignites the fuel mixture. Each cylinder requires a succession of minor explosions to keep your car functioning. The explosions provide the force to move the pistons up and down.

Each cylinder has a precise mixture of fuel and air. The spark plug ignites when the piston rises within the cylinder. The electrical arc generates pressure, which causes the piston to return to the cylinder and spin the engine. As you drive your car, the sequence will continue to replay.

When to Change Spark Plugs

1. The Check Engine Light Turns On.

Your check engine light may illuminate due to worn/failed spark plugs, coil packs, or spark plug wires. According to Firestone Complete Auto Care professionals, if a plug begins to break in today’s vehicles, the check engine light turning on or flashing is the most evident occurrence.

This might cause your engine to misfire and illuminate your check engine light. Our professionals believe a flashing engine light might indicate potentially catastrophic misfires.

In general, it’s preferable to change spark plugs as part of preventative maintenance according to the manufacturer’s recommendations. Driving with misfiring spark plugs can place unnecessary strain on your car’s catalytic converter (the engine’s exhaust cleaner), leading to pricey repairs.

Rough idling, inconsistent power while accelerating, and a rise in exhaust fumes are signs of misfiring spark plugs.

It is important to note that a check engine light can be caused by various issues, not only a spark plug problem. That’s why your neighborhood Firestone Complete Auto Care provides Code Scans, which disclose any codes that indicate a misfire caused by a faulty spark plug. In addition, because we provide comprehensive vehicle maintenance, our experts have the necessary equipment and knowledge in engine control systems, sensors, and onboard diagnostics to run an advanced diagnostic and deliver an accurate repair estimate.

2. Your Car Has Trouble Beginning.

Your spark plugs perform one of the most critical functions in your vehicle: they generate the spark that runs the engine! Old, worn-out spark plugs have a harder time producing the spark that runs your engine. If your automobile stalls when you try to start it, it might be due to faulty spark plugs or broken spark plug wires. The battery is most likely to blame if your automobile has no power and won’t start at all.

3. You’re Replacing the Gas Tank More Often.

Your gas mileage may suffer if your spark plugs are nearing the end of their useful life. In addition, worn-out spark plugs can raise your vehicle’s fuel consumption since they don’t efficiently burn the gasoline that goes into the engine, resulting in more money spent on fill-ups.

According to the National Institute for Automotive Service Excellence, “a misfiring spark plug can lower fuel economy by up to 30%.”

In general, having your automobile kept up can help you save money on gas.

According to, “fixing a car that is visibly out of tune or has failed an emissions test can increase its gas efficiency by an average of 4%.”

4. The Engine Roughly Idles (and You Can Hear It!).

Normally (ideally!), your engine purrs like a cat, but turn down the music and listen. If you hear rattling, pinging, or knocking noises from your engine, your spark plugs might be at fault.

5. Your Car Does Not Accelerate Fast.

You’re probably very comfortable with how your car handles and drives. However, if you find that your automobile isn’t as responsive as it should be, especially while trying to accelerate, it might be due to old spark plugs. It may be time to replace them; no one enjoys driving a slow, gas-guzzling vehicle.

6. The Manufacturer Says It’s Time!

It’s always advisable to stick to the Manufacturer’s Suggested Maintenance Schedule when it comes to automobile upkeep. Examine your vehicle’s recommended maintenance plan to determine when to replace your spark plugs.

Fortunately, spark plugs do not wear out rapidly. They normally have a range of 80,000 miles before needing to be replaced. However, if you observe any of these symptoms, it’s time to examine your spark plugs as part of an engine tune-up.

Driving on worn-out or broken spark plugs might eventually cause engine harm, so don’t put it off.

Should spark plugs be replaced sooner as a precaution?

The distance determines it. For example, if your car’s long-life spark plugs are due at 100,000 miles and your dealer advises changing them at 50,000 miles, it’s too soon. Spark plug with iridium tip Long-lasting iridium-tipped spark plug. If your engine is fuel-efficient and runs like new, consider deferring until it is closer to the optimum mileage.

Is it possible to examine the condition of the spark plugs?

Yes, spark plugs are often tested when an engine misfires, hesitates or fails to operate correctly. An expert technician can learn a lot from the condition of a spark plug. For example, black greasy deposits on a spark plug indicate the presence of oil in the combustion chamber.

A faulty spark plug.

This is common when a car consumes oil between oil changes or is driven largely over short distances, preventing the engine from fully warming up. If one spark plug is fouled, but the others appear OK, the problem is limited to that cylinder.

One sign of clogged spark plugs is when the engine hesitates, sputters, and runs rough at idle or while cold but clears up after revving or traveling on the highway. The faulty spark plugs must be changed, but if the problem persists, the engine must be repaired first.

If a spark plug begins to burn or melt, the cylinder is running hot, either owing to a cooling system malfunction, an abnormally low air-fuel ratio, or detonation. An old spark plug in a decent engine will exhibit no overheating damage and will have a minimal quantity of deposits; it can be gray or brown.

Is it necessary to replace all of the spark plugs at the same time?

Yes, spark plugs are often replaced in pairs. It is critical to utilize the right components, as incorrect spark plugs might create difficulties. It’s also critical to thoroughly check new spark plugs before installing them. The insulator may be shattered if a new spark plug is dropped on a hard surface.

What is the cost of replacing spark plugs?

Conventional spark plugs are reasonably priced ($6-10 per spark plug). Platinum or iridium spark plugs are more expensive ($15-40 per plug). The labor expenses are determined by the engine design. For example, a repair shop may charge $60-$110 for labor to replace spark plugs in a standard 4-cylinder engine, which is very easy. However, access may be problematic with some V6 engines. For example, the intake manifold must be removed to change spark plugs in a Ford Edge or Escape with a V6 engine, raising the labor cost to $260-$320.


A spark plug delivers an electric charge to the engine, igniting the fuel-air combination. Platinum and iridium-containing products are more durable, emitting less heat, generating fewer sparks, and must be changed significantly less frequently.

The primary function of spark plugs is to assist in the engine’s ignition of the fuel-air combination. The more effectively this occurs, the less strain the engine experiences. As a result, there is reduced wear and tear.

As a result, spark plugs play an important part in a performance by regulating how well exhaust gas is discharged from their chamber by minimizing backfires at low rpm and misfiring at high rpm.


Editorial Staff

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