How Long Do Spark Plugs Last? Real Mileage, Signs, and When to Replace

When you think about what keeps your car running, spark plugs, small but critical components that ignite the fuel-air mixture in your engine. Also known as ignition plugs, they’re one of the few parts that fire over 1,000 times per minute while your car is moving. Most modern spark plugs last between 30,000 and 100,000 miles, but that number isn’t set in stone. It depends on the type of plug, your driving habits, and whether your engine is running clean. Copper plugs wear out faster—often around 30,000 miles—while platinum and iridium plugs can go 60,000 to 100,000 miles without issue. But here’s the catch: even if your car still starts, worn spark plugs silently drain fuel economy, reduce power, and can eventually damage your catalytic converter.

That’s why knowing the signs of bad spark plugs, visible symptoms like rough idling, hard starts, or engine misfires matters more than just counting miles. If your car hesitates when you press the gas, or the check engine light flashes, it’s often not the fuel system—it’s the spark. And if you’ve gone over 60,000 miles without checking them, you’re already risking higher fuel bills and unnecessary stress on your engine. engine performance, how smoothly and efficiently your engine runs ties directly to spark plug health. A weak spark doesn’t just make your car sluggish—it can cause unburned fuel to flood into the exhaust, clogging the system over time.

Many drivers wait until their car won’t start before replacing spark plugs. But that’s like waiting for a tire to blow out before checking the pressure. The best approach? Know the typical lifespan for your plug type, watch for the subtle signs, and replace them before they fail. You’ll save money on fuel, avoid costly repairs, and keep your engine running like it should. Below, you’ll find real-world advice from UK drivers and mechanics on what to look for, when to act, and how to avoid the most common mistakes when replacing spark plugs.