What Causes Black Carbon Deposits on Spark Plugs?

[McAlexa]

Spark plug black carbon deposits are most commonly caused by poor combustion. This blackened substance is formed by carbon buildup and burning engine oil. How spark plugs work: Under high voltage, the air between the spark plug's center electrode and side electrode rapidly ionizes, forming positively charged ions and negatively charged free electrons. When the voltage between electrodes reaches a certain level, the number of ions and electrons in the gas increases like an avalanche, causing the air to lose its insulating properties and forming a discharge channel, resulting in a "breakdown" phenomenon. At this point, the gas becomes a luminous body, creating a "spark." Accompanying this is thermal expansion and a "crackling" sound. The temperature of this electrical spark can reach 2000-3000°C, sufficient to ignite the air-fuel mixture in the cylinder combustion chamber. Spark plug replacement intervals: Under normal maintenance conditions, spark plugs should be replaced every 40,000 to 60,000 kilometers. However, this may vary depending on the brand and engine type, so it's recommended to follow the owner's manual. The following standards can be used as reference for maintenance replacement: Platinum spark plugs should be replaced at 40,000 km, standard nickel alloy spark plugs at 20,000 km, and iridium spark plugs at 60,000-80,000 km.