Spark Plug Life: How Long They Last and When to Replace Them

When your engine sputters, stalls, or loses power, the culprit might be something small but critical: the spark plug, a small component that ignites the air-fuel mixture in your engine’s cylinders. Also known as ignition plug, it’s one of the few parts in your car that fires thousands of times every minute. Even though it’s tiny, its failure can wreck your fuel economy, trigger the check engine light, or even damage your catalytic converter. Most spark plugs last between 30,000 and 100,000 miles, depending on the type—copper ones wear out faster, while platinum or iridium plugs can go much longer. But mileage isn’t the only factor. Driving habits, fuel quality, and engine condition all play a role. If you’re constantly idling, short-tripping, or running cheap gas, your spark plugs won’t last as long as the manual says.

That’s why knowing the spark plug symptoms, the early warning signs that your plugs are failing is more important than sticking to a fixed schedule. Hard starts, rough idling, poor acceleration, and a noticeable drop in gas mileage are all red flags. The engine misfire, when one or more cylinders fail to ignite properly is the most common sign. It’s not just annoying—it can overheat your exhaust system and lead to expensive repairs. And if you ignore it, you might end up replacing a $200 catalytic converter instead of $50 spark plugs.

Many people wait until their car won’t start to think about spark plugs. But by then, it’s often too late. The best time to replace them is before they fail—especially if you’ve hit the 60,000-mile mark and your car doesn’t feel as crisp as it used to. Checking them yourself takes ten minutes. You don’t need fancy tools, just a socket wrench and a little patience. And if you’re unsure, look at your owner’s manual or check the part number on the old plug. Matching the right type matters. Using the wrong one can cause overheating, pre-ignition, or even piston damage.

Below, you’ll find real-world guides that show you exactly what to look for when your spark plugs are dying, how to test them, and how to avoid the most common mistakes people make when replacing them. Whether you’re trying to save money, fix a rough-running engine, or just understand why your car feels off, these posts give you the facts—not the fluff.