The short answer
Spark plugs commonly last anywhere from roughly 20,000 miles to over 100,000 miles. The wide range comes mostly from the plug material and the engine. The most reliable number for your car is the interval in your owner’s manual, because it was set for your engine and plug type.
Lifespan by plug type
Published figures differ between sources, so treat these as general ranges.
- Copper (nickel alloy): the shortest life, often cited at roughly 20,000 to 40,000 miles.
- Platinum: longer, commonly cited at around 60,000 to 100,000 miles, with some sources quoting less for basic platinum.
- Iridium: often the longest, commonly cited at about 75,000 to 100,000 miles or more, and some modern engines specify longer intervals.
If you are choosing a replacement, see how to choose the right spark plugs for your car.
What changes how long plugs last
- Engine design: turbocharged and high-compression engines are harder on plugs, and some manufacturers call for earlier changes.
- Driving habits: lots of short trips, heavy stop-and-go driving, towing and hard use can increase wear and deposits.
- Engine condition: oil leaking into a cylinder or a rich fuel mixture can foul plugs early.
- Fuel and maintenance: poor fuel quality or neglected maintenance can shorten service life.
- Plug quality and fit: a plug with the wrong heat range or gap may wear unevenly. See spark plug heat range explained.
Signs plugs are wearing out
Replacement is sometimes needed before the scheduled interval. Watch for:
- Rough idle or shaking
- Hesitation or sluggish acceleration
- Hard starting
- Poorer fuel economy
- A flashing or lit check engine light (see flashing vs. solid check engine light)
These symptoms overlap with other problems, such as failing ignition coils or fuel issues. The full list, with how to tell them apart, is in bad spark plug symptoms and what you’ll notice.
Who can replace them
Many independent repair shops and dealerships replace spark plugs, and some quick-lube chains may as well, though services differ by location, so call ahead. Some people do the job themselves on engines where the plugs are easy to reach. If you do, follow the torque specification for your plugs, since over- or under-tightening can cause damage.
Do you need to replace them?
If you are near or past the manual’s interval, yes, it is generally sensible to do so even if the car seems fine, since wear is gradual and easy to miss. If you are well within the interval and the car runs well, there is usually no need to replace them early. Plugs also show up around the 60,000 and 90,000-mile marks in a typical car maintenance schedule. For the bigger picture of what new plugs and wires can and cannot improve, read our guide to spark plug and wire replacement.