Spark plugs are installed on the side or top of the engine. In the early days, spark plugs were connected to the power distributor through cylinder wires. In the past decade, engines in small cars have mostly been changed to have ignition coils directly connected to spark plugs. The working voltage of the spark plug is at least 10000V, and the high-voltage electricity is generated by the ignition coil from 12V electricity, which is then transmitted to the spark plug.

The replacement cycle of spark plugs is directly related to their material. The replacement cycle of nickel alloy spark plugs is 20000 to 30000 kilometers, nickel yttrium alloy spark plugs are 30000 kilometers, single platinum spark plugs are 40000 kilometers, double platinum spark plugs are 60000 kilometers, iridium spark plugs are 80000 kilometers, and platinum iridium alloy spark plugs can reach 100000 kilometers.