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

When you think about your car’s engine, you probably don’t picture the tiny spark plug, a small but critical component that ignites the fuel-air mixture in the engine cylinder. Also known as a ignition plug, it’s the spark that makes your engine run—no spark, no drive. Most people don’t think about spark plugs until the engine starts misfiring, sputtering, or refusing to start. But ignoring them isn’t just inconvenient—it can lead to bigger, costlier problems down the line.

The spark plug lifespan, how long a spark plug can reliably fire before it needs replacing isn’t the same for every car. Standard copper plugs might last 20,000 to 30,000 miles, while platinum or iridium ones can go 60,000 to 100,000 miles. What matters more than mileage is how you drive. Short trips with lots of cold starts? That’s hard on plugs. Constant highway driving? They’ll last longer. Engine oil leaks, rich fuel mixtures, or bad ignition coils can also shorten their life. You don’t need a diagnostic tool to spot trouble—listen for rough idling, notice if your car hesitates when you press the gas, or check if fuel economy has dropped. These aren’t just symptoms—they’re warnings from your ignition system, the network of parts that delivers the spark to the combustion chamber that something’s off.

Replacing spark plugs isn’t rocket science, but it’s not a "set it and forget it" task either. Skipping replacement can cause misfires, which lead to unburned fuel entering the exhaust. That can damage your catalytic converter—a repair that costs five times more than a spark plug change. And if you wait too long, the plug can seize in the cylinder head, turning a simple job into a major engine repair. Even if your car’s manual says "100,000 miles," if you notice any of those signs, don’t wait. A quick inspection at 60,000 miles can save you time, money, and frustration.

What you’ll find below are real-world stories and guides from drivers who’ve dealt with worn plugs, misfires, and unexpected breakdowns. You’ll learn how to spot early signs of failure, what types of plugs work best for Indian driving conditions, and why some people replace theirs every 40,000 miles—even when the manual says longer. No theory. No fluff. Just what works.