How Long Do Spark Plugs Last?

Quick Answer

Spark plugs typically last between 30,000 and 100,000 miles — about 2 to 8 years for a typical driver — depending on the material. Standard copper plugs wear out fastest (around 30,000 miles), while long-life iridium plugs can go 80,000–100,000+ miles. Always check your owner's manual for the manufacturer's recommended interval, because engine design and driving conditions matter as much as the plug material.

Spark Plug Lifespan by Type

The electrode material is the single biggest factor in how long a spark plug lasts. Precious metals like platinum and iridium resist erosion far better than copper.

Plug Type	Typical Lifespan	Best For
Copper / Nickel	20,000–40,000 miles	Older engines, high-performance applications
Single Platinum	60,000–70,000 miles	Modern daily drivers
Double Platinum	60,000–100,000 miles	Waste-spark ignition systems
Iridium	80,000–100,000+ miles	Newest vehicles, best longevity
Ruthenium (newest)	100,000+ miles	Latest premium plugs

How to Tell Your Spark Plugs Are Worn

Even before you hit the mileage interval, worn plugs give warning signs:

• Rough idle or a shaky, uneven engine at a stop
• Trouble starting the engine, especially in cold weather
• Engine misfires — a stumbling or hesitating feeling under acceleration
• Poor fuel economy — worn plugs burn fuel less efficiently
• Check engine light with misfire codes (P0300–P0308)
• Sluggish acceleration and reduced power

Factors That Affect Spark Plug Life

Driving Conditions

Stop-and-go city driving, frequent short trips, and towing heavy loads all shorten plug life. Highway cruising is gentler on plugs.

Engine Condition

An engine that burns oil or runs rich (too much fuel) will foul plugs faster, coating them with deposits that reduce their effective lifespan.

Fuel Quality

Low-quality fuel and carbon-heavy additives leave deposits on the electrode, reducing performance over time.

Plug Gap

As the electrode erodes, the gap widens, forcing the ignition coil to work harder. An out-of-spec gap accelerates wear and can damage coils.

How to Make Spark Plugs Last Longer

• Use the manufacturer-recommended plug type — don't downgrade to copper in an engine designed for iridium
• Fix oil leaks and rich-running conditions promptly to prevent fouling
• Use quality fuel to minimize carbon deposits
• Replace all plugs at once, not one at a time, so they wear evenly
• Apply anti-seize sparingly only if the manufacturer recommends it (many iridium plugs should be installed dry)
• Have the ignition system inspected during regular service intervals

When to Replace Them

Even if your plugs haven't reached their mileage limit, replace them if you notice misfires, hard starts, or a drop in fuel economy. Replacing spark plugs is relatively inexpensive compared to the cost of a damaged catalytic converter or ignition coil caused by running on worn plugs. A typical replacement costs $40–$150 for parts and $100–$250 in labor depending on engine access.

Bottom Line

Check your owner's manual for the exact interval, but as a rule of thumb: copper plugs every 30,000 miles, and platinum or iridium plugs every 60,000–100,000 miles. Watch for the warning signs, and don't wait until a plug fails completely.