Spark Plug Lifespan: How Long Do They Last and When to Replace Them
When your car sputters, stalls, or feels sluggish, the culprit might be something small but critical: your spark plugs, tiny but vital components that ignite the fuel-air mixture in your engine's cylinders. Also known as ignition plugs, they’re the reason your engine starts and keeps running. Most modern spark plugs last between 60,000 and 100,000 miles, but that’s not a guarantee—driving habits, fuel quality, and engine condition can shorten that life dramatically.
Ignoring worn spark plugs doesn’t just hurt fuel economy—it can damage your catalytic converter, cause misfires, and even lead to engine knocking. A failing spark plug doesn’t always throw a warning light. You’ll notice it in the way your car behaves: rough idle, hesitation when accelerating, or a noticeable drop in mileage. These aren’t just annoyances—they’re signs your engine isn’t getting the spark it needs. Related to this are engine performance, how efficiently your engine converts fuel into power, and car maintenance, the routine checks that prevent small problems from becoming expensive repairs. If your car’s over 60,000 miles and you haven’t checked the plugs, you’re already risking performance.
It’s not just about mileage. If you drive mostly short trips in stop-and-go traffic, your plugs wear out faster. Cold starts, poor fuel quality, or a rich air-fuel mixture can coat the electrodes and kill the spark. That’s why some mechanics recommend checking them every 30,000 miles, especially if you’re in the UK where damp weather and frequent short drives are the norm. You don’t need a diagnostic tool to spot bad plugs—many symptoms show up in how your car feels. Rough idling? That’s one. Hard starts? That’s another. A sudden drop in fuel economy? That’s often the first clue.
Replacing spark plugs isn’t a complex job, but it’s one many drivers skip because they assume it’s expensive or requires a garage. In reality, the parts cost less than £30, and with basic tools, you can do it yourself in under an hour. The real cost is ignoring them—because when spark plugs fail, they don’t just make your car run poorly. They can cause long-term damage to your engine’s internals. That’s why knowing the spark plug lifespan isn’t just about maintenance—it’s about protecting your investment.
Below, you’ll find real-world guides on how to spot failing spark plugs, whether replacing them actually improves performance, and how they connect to other systems like fuel economy and engine efficiency. No fluff. Just clear, practical advice from drivers who’ve been there.
