What are the signs that spark plugs need to be replaced?

[MacVincent]

Signs that spark plugs need replacement: The car exhibits symptoms such as difficulty starting, low power, excessive exhaust emissions, and increased fuel consumption; severe damage to the spark plugs, with phenomena like 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. Assess the condition of the spark plugs based on their appearance and color. Normal spark plugs have an insulator skirt and electrodes that 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 plugs are contaminated with 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. After troubleshooting, replace the spark plugs with new ones. Additionally, if the spark plugs appear 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.