Spark Plugs: Engine-Ignition System View

Spark plugs ignite the fuel-air mixture at the exact moment the ECU commands. Their job sits at the end of the ignition system — coil generates a high-voltage pulse, the plug discharges the pulse across its gap, the spark ignites the mixture. Get the plug wrong and the ignition system can compensate up to a point, but eventually you see misfires, fault codes and reduced economy.

Heat range and electrode

Heat range determines how quickly the plug dissipates heat into the head. A plug too hot for the engine pre-ignites; a plug too cold for the engine fouls. Each engine has a defined heat range; match by OE part number.

Electrode material: copper, platinum, iridium. Iridium and platinum last longer because the precious metals erode more slowly at the spark point. Most modern OE plugs are iridium or platinum.

Brand

NGK is OE on most Japanese and Korean engines. Bosch is OE on most European. Denso supplies Toyota and many others. Beru is OE on premium German performance applications.

Find spark plugs for your engine on the Spark Plugs (Engine Parts) collection.