Decoding Spark Plug Part and Stock Numbers

Did you know every NGK spark plug has both a plug number and a stock number? Only the plug number is labeled on the spark plug, while both are printed on the box. The plug number is used to decode the spark plug and the stock number is used by our sales associates to aid in stock management, as alphanumeric numbers are harder to inventory. The stock number is a random 3-, 4- or 5-digit number and has no relation to heat range or plug type.

An example is DPR5EA-9; 2887.

DPR5EA-9 is the plug number and 2887 is the stock number.

The exception to this is racing plugs. An example of an NGK racing plug is R5671A-11. Here, R5671A represents the plug type and -11 represents the heat range. The stock number is 6596.

NGK lists a design symbols chart in the front of every spark plug catalog.