At what mileage should spark plugs be replaced?

Typical replacement intervals by plug type

These guidelines reflect common industry expectations and are intended as a starting point. Exact figures vary by manufacturer and plug design.

• Conventional copper spark plugs: about 30,000 miles (48,000 km).


• Platinum-tipped spark plugs: about 60,000 miles (96,000 km).


• Iridium spark plugs: about 60,000 to 120,000 miles (96,000 to 193,000 km).


• Long-life/low-maintenance plugs used in many modern engines: up to around 100,000 miles (160,000 km), with some models reaching 120,000 miles (193,000 km).

Manufacturers may push these numbers higher or lower depending on the engine and the specific plug design. Always verify with the owner’s manual or dealer service schedule.

Situational factors that can shorten or extend life

Even if your car is within the nominal mileage window, real-world driving can change when plugs need replacement. Consider these conditions and behaviors.

• Frequent short trips or extensive idling that prevents the engine from reaching optimal operating temperature.


• Heavy fuel quality issues or deposits from oil leaks or rich fuel mixtures.


• High-compression or turbocharged engines that generate more heat and faster wear.


• Worn ignition wires, coils, or injectors that increase wear on plugs or cause misfires.

When in doubt, a professional inspection can determine whether plugs should be replaced based on observed wear, electrode gap, and engine performance.

Signs you may need to replace plugs sooner

Look for symptoms indicating spark plug wear before you reach the nominal mileage.

• Engine misfires or rough idling


• Difficulty starting or longer cranking times


• Loss of acceleration or reduced power


• Decreased fuel economy and higher emissions


• Visible wear, fouling, or damage on plug electrodes (when inspected)

If you notice these symptoms, schedule a diagnostic check. Replacing worn plugs may restore performance and efficiency, and it’s often recommended to inspect ignition wires/coils and related components at the same time.

Summary: For most drivers, plan to replace spark plugs per the material type—about 30k miles for copper, 60k for platinum, and 60k–120k for iridium—with some long-life designs extending to 100k–120k miles. Always follow the vehicle’s manual and be mindful of driving conditions that can shorten plug life. Regular maintenance and timely replacement help maintain engine performance and fuel efficiency.

How do I know when my spark plugs need replacing?

You know your spark plugs need replacing if you experience signs of poor engine performance such as a rough idle, difficulty starting, or engine misfires, and reduced fuel economy. Other indicators include slow acceleration, engine knocking, and the "check engine" light coming on. 
Performance and starting issues

• Engine misfires: The engine may feel like it's skipping a beat, stuttering, or shaking while running. 
• Rough idle: The engine runs roughly or shakes noticeably when the car is stopped. 
• Difficulty starting: The engine turns over for a longer time than usual before starting, or the car may not start at all. 
• Poor acceleration: The car feels sluggish and doesn't accelerate as quickly as it used to. 
• Engine knocking: You may hear a "pinging" or "knocking" sound from the engine, especially when accelerating. 

This video demonstrates how to read a spark plug to determine its condition: 57sMotorWeekYouTube · Apr 4, 2019
Efficiency and warning indicators

• Reduced fuel economy: You may find yourself at the gas pump more often, as worn spark plugs can lead to incomplete combustion and wasted fuel. 
• "Check Engine" light: A persistent "check engine" light can indicate a misfire or other engine problems caused by bad spark plugs. 
• Unusual smells: A strong smell of unburned fuel from the exhaust can signal a combustion problem. 

This video explains when it is necessary to replace spark plugs: 0:16Wrenching MafiaYouTube · Jan 3, 2024
How to confirm

• Check your owner's manual: The most reliable way to know your replacement schedule is to check your vehicle's owner's manual for the manufacturer's recommended replacement interval. 
• Perform a visual inspection: You can remove the spark plugs for a visual check. Look for signs of wear, like erosion on the electrode, or damage such as cracks in the ceramic insulator. 
• Scan for codes: Use an OBD-II scanner to check for diagnostic trouble codes, such as those in the P0300 series, which specifically indicate a misfire. 

How long do spark plugs usually last?

Spark plugs typically last between 30,000 and 100,000 miles, but the exact lifespan depends on the type of plug. Conventional copper plugs may need replacing every 20,000-30,000 miles, while platinum and iridium plugs can last much longer, up to 60,000 or even 100,000 miles. Always check your vehicle's owner's manual for the manufacturer's recommended replacement interval. 
Spark plug lifespan by type

• Conventional (Copper): 20,000 to 30,000 miles
• Platinum/Iridium: 60,000 to 100,000+ miles 

Other factors that affect lifespan

• Driving habits: Frequent short trips or stop-and-go traffic can reduce lifespan.
• Fuel quality: Using poor-quality fuel can lead to carbon buildup on the plugs.
• Vehicle maintenance: Problems with the ignition system can cause premature wear. 

Signs your spark plugs need replacing
Engine misfires or rough idling, Decreased fuel efficiency, Difficulty starting the engine, Increased fuel consumption, and The check engine light is on.

How much would a mechanic charge to change my spark plugs?

How much does it cost for a professional spark plug replacement? If it's a task you aren't comfortable doing on your own, spark plug replacement cost at a repair shop will have labor costs higher than the parts. For instance, a set of four spark plugs in a compact car will likely be around $50 to $80 to install.

Should I change spark plugs at certain mileage or wait for failure?

At 130000 miles you should plan to replace spark plugs unless the manufacturer explicitly specifies a longer interval and you have documented recent replacement. If plugs are original and rated for less than or near 130k, replace them now to avoid misfires, poorer fuel economy, and possible downstream damage.