Spark plugs are small, cheap and easy to forget, yet they light the fuel in every cylinder thousands of times a minute. Worn plugs quietly cost you smoothness, power and fuel economy.
How long they last
It depends on the type. Copper plugs may last around 30,000 miles, while platinum and iridium plugs can go 60,000 to 100,000 miles. Always follow the interval in your owner manual for the plugs your car uses.
Signs they are worn
- A rough idle or occasional misfire.
- Slower acceleration and worse fuel economy.
- Hard starting, especially when cold.
- A check engine light for a misfire.
Why the type matters
Fitting the plug type and heat range your engine was designed for matters. The wrong plug can foul, misfire or even cause damage over time, so match the specification rather than just the thread size.
Frequently asked questions
Can I replace just one spark plug?
You can in an emergency, but replacing the full set keeps the engine running evenly, since they wear at a similar rate.
Do new spark plugs improve performance?
If the old ones were worn, yes, you get back smoother running and better economy. They do not add power beyond the original design.
See our car accessory guides for tools and tune up parts.
