Spark plug info
Technical guides and reference decoding: everything to understand and choose a spark plug.
Technical guides
- How to read a Bosch spark plug referenceEach letter and number in a Bosch code is coded: thread & seat, type, resistor, heat range, reach, electrode and gap. Here is how to decode it.
- How to read a Denso spark plug referenceA Denso code encodes the electrode material, thread & seat, heat range, reach and gap. Here is how to decode it.
- How to read a Beru spark plug referenceA Beru technical code encodes the thread & seat, resistor, heat rating, reach, electrode and material. Here is how to decode it.
- How to read a Brisk spark plug referenceBrisk's Identification System encodes the shell (thread, reach, hex, seat), resistor, heat range, spark-gap design, electrode material and gap. Here is how to decode it.
- How to read a Torch spark plug referenceTorch codes combine a shell letter (thread & reach, ISO sizes), a heat-range number, a resistor mark and design-symbol letters for the tip and electrode material. Here is how to read them.
- How to read a Magneti Marelli spark plug referenceA Magneti Marelli short code encodes the range, the electrode type, the thread & hex size, the heat grade and the gap. Here is how to decode it.
- How to read an Eyquem spark plug referenceAn Eyquem code encodes the resistor, the shell/thread, the electrode material, the heat range, the reach, the seat, the insulator nose and the ground electrodes. Here is how to decode it.
- How to read an ACDelco spark plug referenceACDelco identifies plugs by a part number plus a specification sheet (dimensions). Here is how to read the code and the ranges.
- How to read a Champion spark plug referenceEach letter and number in a Champion code is coded: resistor, thread diameter, reach, heat range, firing end and gap. Here is how to decode it.
- How to read an NGK spark plug referenceEvery letter and number in an NGK code is coded: thread diameter, reach, heat range, electrode and gap. Here is how to decode it.
- What is a spark plug heat range?The heat range is how fast the plug sheds heat: "hot" retains heat, "cold" dissipates it quickly.
- Spark plug thread (diameter)The thread is the screw diameter (e.g. 14 mm); it must match the cylinder head exactly.
- Reach (thread length)The reach is the threaded length (e.g. 19 mm); wrong reach harms combustion and can damage the engine.
- Electrode gapThe gap is the distance where the spark jumps (e.g. 0.8 mm); it is set per engine.
- Electrode: nickel, platinum or iridium?The centre electrode material (nickel, platinum, iridium) drives longevity and spark quality.
- Resistor (RFI-suppressed) spark plugA resistor plug contains a resistor that suppresses electrical interference.
- Seat typeThe seat is the sealing shape: flat (with gasket) or tapered.
- Spark plug wrench sizeThe hex size (e.g. 20.8 mm / 16 mm) for fitting and removing the plug.