Most modern cars need new spark plugs roughly every 30,000–100,000 miles, depending on plug type and your vehicle’s specific service schedule. Always trust your owner’s manual first, then adjust based on how and where you drive.

Quick Scoop

  • For many cars, spark plugs are changed about every 30,000–60,000 miles for basic copper plugs. Premium platinum or iridium plugs can often last 60,000–100,000 miles or more if the engine is healthy.
  • Your owner’s manual gives the official interval; some models specify around 60,000 miles while others stretch to 100,000–120,000 miles.
  • Replace them sooner if you notice symptoms like rough idle, misfires, sluggish acceleration, or worse fuel economy, even if you have not hit the mileage interval yet.

What Actually Controls The Interval

  • Plug type matters:
    • Copper: shorter life, often around 20,000–30,000 miles.
* Platinum/iridium: longer life, often 60,000–100,000+ miles.
  • Driving style matters: lots of short trips, idling, or very hot operation can wear plugs faster than steady highway driving.
  • Vehicle design matters: some manufacturers deliberately set long intervals (100,000+ miles) on long‑life plugs, others keep more conservative schedules.

Simple Rule Of Thumb

  • Check your manual, then:
    1. If it calls for copper plugs, plan roughly every 30,000 miles.
    2. If it calls for platinum or iridium, plan somewhere around 60,000–100,000 miles.
    3. If you buy a used car and don’t know the history, having the plugs inspected or replaced pre‑emptively is often cheap insurance against hard starts and misfires.

Bottom line: “how often should you replace spark plugs” is usually answered by “whatever your manual says, typically in the 30k–100k mile range, adjusted for plug type and driving conditions.”

TL;DR: Most drivers are safe changing spark plugs around the manufacturer’s interval, usually between 30,000 and 100,000 miles, or earlier if performance starts to drop.

Information gathered from public forums or data available on the internet and portrayed here.