Spark Plug Lifespan: How Long Do They Last?

Ever wondered why your engine sometimes stutters or your fuel gauge seems off? In many cases the culprit is a worn‑out spark plug. Knowing how long spark plugs should last helps you avoid costly breakdowns and keeps your car running smooth.

Factors That Affect Spark Plug Life

Not all spark plugs are created equal. Copper plugs are cheap and usually need replacing every 20‑30 k miles, while iridium or platinum plugs can stretch to 60‑100 k miles. The material you choose sets the baseline, but several real‑world factors move the needle.

Driving style matters a lot. If you rev hard, race, or frequently drive in stop‑and‑go traffic, the plugs experience more heat cycles and wear faster. On the other hand, steady highway cruising is easy on them.

Engine condition also plays a role. A poorly tuned engine may run too rich or too lean, both of which can foul plugs quicker. Keep your fuel system clean and get regular tune‑ups to give your plugs a longer lease.

Fuel quality is another hidden factor. Low‑octane or contaminated fuel can leave deposits on the electrode, shortening lifespan. Using the recommended fuel grade for your car is a simple way to protect your plugs.

When to Replace Your Spark Plugs

Most manufacturers set a mileage interval, but real‑time symptoms tell the story better. If you notice rough idling, a drop in power, or a hard start, it’s time to check the plugs.

Look for visible signs: black carbon buildup, cracked insulators, or worn electrodes. Even a small gap change can weaken the spark and hurt fuel efficiency.

One practical tip is to do a quick spark plug test during routine oil changes. Pull the plug, inspect it, and compare it with the new one in the box. If it looks worse than the new plug, replace it before you hit the next mileage milestone.

Keeping a log helps too. Write down the mileage when you install a new set and set a reminder for the next interval. That way you won’t rely just on guesswork.

Finally, consider the cost‑benefit angle. A set of iridium plugs may cost more upfront, but if you drive a lot they often pay for themselves by lasting double the time of copper plugs.

Bottom line: understand the type of plug you have, watch for performance changes, and stick to a realistic replacement schedule. With a little attention, you’ll keep your engine firing on all cylinders and avoid surprise trips to the garage.