How often should I change spark plugs?
Typical replacement intervals
Spark plug life varies widely by material and engine design. Copper plugs are the shortest-lived, often needing replacement every 20,000 to 30,000 miles. Platinum plugs typically last 60,000 miles, while iridium and double-platinum plugs can go 100,000 miles or more. Always follow the manufacturer's recommendation in your owner's manual or maintenance schedule, as some engines are harder on plugs than others.
- Copper: 20,000–30,000 miles
- Platinum: 60,000 miles
- Iridium: 100,000 miles or more
- Always check owner's manual for exact interval
Signs you need new plugs
Even if you haven't reached the recommended interval, certain symptoms suggest worn plugs. These include rough idle, misfires (especially under load), reduced fuel economy, and difficulty starting. A check engine light with a P0300-series code often points to ignition problems. If you pull a plug and see heavy deposits, worn electrodes, or cracked porcelain, replace them regardless of mileage.
Factors that affect plug life
Driving habits and conditions matter. Short trips and stop-and-go driving can foul plugs faster, while highway driving is easier on them. Engine modifications, like turbocharging or nitrous, can also shorten plug life. Using the wrong heat range or gap can cause premature wear or damage. Always use the plug type and gap specified by the manufacturer.
- Short trips accelerate wear
- High-performance engines may need more frequent changes
- Wrong gap or heat range can damage plugs
- Check plugs during other maintenance for condition
Common mistakes
- Waiting for symptoms: by the time you notice misfires, the plugs may have been worn for thousands of miles, hurting fuel economy and catalytic converter life.
- Using the wrong plug type: not all iridium plugs are the same; using a plug not specified for your engine can cause misfires or damage.
- Over-torquing or under-torquing: incorrect torque can lead to broken plugs or compression leaks; always use a torque wrench.
