Should spark plugs be replaced based on time or mileage?
2 Answers
Spark plugs are typically replaced based on mileage. Under normal maintenance conditions, they should be replaced after driving 40,000 to 60,000 kilometers. However, this may vary depending on the brand and engine type, so it's recommended to follow the user manual. Platinum spark plugs should be replaced at 40,000 kilometers, ordinary nickel alloy spark plugs at 20,000 kilometers, and iridium spark plugs at 60,000 to 80,000 kilometers. Methods to determine if a spark plug is damaged: Remove the spark plug and observe its appearance to assess its condition. A normal spark plug's insulator skirt and electrodes should appear gray-white, gray-yellow, or light brown. A properly functioning spark plug has a reddish-brown insulator skirt, with an electrode gap between 0.8-0.9mm and no signs of electrode burning. If the spark plug is covered in oil or deposits but not damaged, it can continue to be used after cleaning off the oil and deposits. If the spark plug is severely damaged, with signs such as blistering at the top, black streaks, cracks, or melted electrodes, the cause of the damage should be identified. After troubleshooting, replace the spark plug with a new one. Additionally, if the spark plug appears black as if smoked, it indicates that the wrong heat range was selected or that the air-fuel mixture is too rich, with oil creeping up.
My mechanic told me that spark plug lifespan can't be judged solely by time or mileage. For cheap nickel-alloy spark plugs, the electrodes wear out after just 20,000 km – even if you only drive 5,000 km a year, they should be replaced by the third year. But long-life iridium or platinum spark plugs can easily last 80,000 km. However, once my car started idling roughly at just 30,000 km, and upon inspection, the ignition ceramic was cracked – this kind of unexpected aging has nothing to do with mileage. So, the intervals in the maintenance manual are just guidelines. Pay attention to whether your car has difficulty starting or a sudden increase in fuel consumption. If you notice any issues, don't hesitate to check the spark plugs immediately.
