Spark plugs made of precious metals are better. The spark plug is a crucial component in the ignition system of a gasoline engine. It introduces high-voltage electricity into the combustion chamber, causing it to jump across the electrode gap and generate a spark, thereby igniting the combustible air-fuel mixture in the cylinder. The spark plug mainly consists of a terminal nut, insulator, terminal stud, center electrode, side electrode, and shell. The main types of spark plugs include: standard spark plugs, extended insulator spark plugs, electrode-type spark plugs, seat-type spark plugs, pole-type spark plugs, and surface-gap 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 in the gap, resulting in a "breakdown" phenomenon. At this point, the gas becomes a luminous body, known as a "spark." Along with the heat expansion, a "snapping" sound is produced. The temperature of this electric spark can reach 2000–3000°C, which is sufficient to ignite the air-fuel mixture in the cylinder's combustion chamber.
