NGK REFERENCE - Spark Plugs An NGK code reads left to right and tells you almost everything about the plug. The opening letters give the thread and the construction type, B, BKR, BCPR, ZFR, IFR, PFR or LKR among others. The digit that follows is the heat range: the higher it is, the colder the plug, and a tuned engine almost always calls for a step colder. The letters after that describe the technology, iridium or platinum in particular, and the segment beyond the dash usually corresponds to the gap. Eight hundred and sixty-one part numbers are active on this page. None is tied to a vehicle: selection is by code, read off the plug you removed.
