When Should Spark Plugs Be Replaced?
2 Answers
The extent to which spark plugs need replacement: Severe damage to spark plugs, with phenomena such as blistering, black streaks, cracking, or electrode melting at the top. Methods to determine if spark plugs are damaged: Remove the spark plugs and observe them to assess their condition based on the following appearance colors. Normal spark plugs have a skirt insulator and electrodes that appear gray-white, gray-yellow, or light brown. A properly functioning spark plug has a skirt insulator that is reddish-brown, with an electrode gap between 0.8-0.9mm and no signs of electrode burning. If the spark plugs are covered in oil or deposits but are not damaged, they can continue to be used after cleaning off the oil and deposits. If the spark plugs are severely damaged, with blistering, black streaks, cracking, or electrode melting at the top, the cause of the damage should be identified, the fault rectified, and new spark plugs replaced. Additionally, if the spark plugs appear black as if smoked, it indicates that the wrong heat range was selected for the spark plugs, the air-fuel mixture is too rich, or engine oil is leaking into the combustion chamber.
I've been driving for over ten years, and whether to replace spark plugs mainly depends on the specific condition. Generally, follow the maintenance manual—new cars might need replacement every 30,000 to 40,000 kilometers, but older cars should be serviced earlier. If the engine starts shaking, especially with unstable idle speed, that's a clear signal. I've also experienced slower acceleration, feeling the car struggles when climbing, or a sudden increase in fuel consumption—all could indicate spark plug issues. When inspecting the electrodes, excessive wear, gaps exceeding standards, or thick carbon buildup are signs they need replacing. Don't wait until ignition failure occurs; timely replacement saves fuel and ensures safety. Many modern cars have extended spark plug lifespans, but if the engine light comes on or there's delayed starting, it's time to visit a professional shop.
