Does a brick-red spark plug need to be replaced?
2 Answers
If the spark plug is reddish-brown or has a rust-colored brick-red appearance, it indicates normal combustion and does not require replacement. Working principle of spark plugs: Under high voltage, the air between the center electrode and the side electrode of the spark plug rapidly ionizes, forming positively charged ions and negatively charged free electrons. When the voltage between the 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 forms a luminous body, known as a "spark." Along with the heat expansion, a "crackling" sound is also produced. The temperature of this electric spark can reach as high as 2000-3000°C, which is sufficient to ignite the air-fuel mixture in the combustion chamber of the cylinder. Criteria for determining spark plug damage: Damaged spark plugs may exhibit the following symptoms: difficulty starting, reduced power, excessive exhaust emissions, and increased fuel consumption.
I just helped a friend check his car the other day, and his spark plugs were also brick-red in color, which is indeed a telltale sign. A brick-red hue typically indicates excessively high combustion chamber temperatures or a lean fuel mixture—meaning an imbalance in the air-to-fuel ratio. This can cause the spark plugs to overheat and accumulate oxidized deposits, potentially shortening their lifespan in the long run. Ignoring it may lead to premature aging of the spark plugs and even trigger issues like engine misfires or increased fuel consumption. My advice is to first inspect the air-fuel ratio or oxygen sensors for faults, and replace the spark plugs if necessary to prevent bigger problems. After all, replacing a small spark plug is far more cost-effective than repairing an engine, and it can even improve ignition efficiency. Don’t wait until the car breaks down to regret it—having a mechanic take a quick look during routine maintenance is the most hassle-free approach.
