Spark plugs differ in the following aspects:
Thread diameter
The common thread sizes are M10, M12, and M14. Classic vehicles usually use M14 threads. 4-stroke and modern 2-stroke engines with injection systems typically use the smaller M10 or M12 spark plugs.
Heat range
The heat range determines a spark plug's thermal durability and self-cleaning effect. There are “cold” and “hot” spark plugs.
Cold plugs are used in high-performance engines with high combustion temperatures. Hot plugs are used in low-load stock engines. Hot types heat up quickly and burn off soot more effectively.
Heat resistance is influenced by insulator design. Cold plugs dissipate heat well; hot plugs retain more heat. Heat range doesn’t indicate power or strength. A cold plug in a weak engine may foul, while a hot plug in a race engine may overheat and cause damage.
Heat range codes vary by manufacturer.
Electrode material
Common materials include copper, platinum, silver and iridium.
Copper is the most used, followed by silver and platinum. Precious metal plugs are more expensive due to material costs.
The main impact of the material is wear resistance. Ultra-thin iridium electrodes (Ø=0.6 mm) also improve ignition voltage and combustion efficiency.
DE | €
