heat rating
also called heat range · how hot the plug runs
How fast the plug carries heat out of its firing end — the single most consequential number on a spark plug, because too hot pre-ignites and too cold fouls. Published by every maker as its own catalogue column (NGK heads it "Heat rating"; Bosch heads its equivalent "Heat range code number"). It is a TOKEN and not a numeral, for two reasons that are both visible on the makers' own pages. First, Bosch publishes 06, 07, 08 and 09 as entries distinct from 6, 7, 8 and 9 — a numeral cannot hold a leading zero, so the rating is a code. Second, the number is not on a shared measurement axis at all: NGK's runs 2 to 10, Denso's 9 to 31, Bosch's 06 to 13, and NGK and Denso count upwards towards COLDER while Bosch and Champion count upwards towards HOTTER. It is therefore qualified by `heat_range_scale`, REQUIRED, so that a bare number can never be compared across makers — the b154 `viscosity_grade` / `grading_scale` shape, minted here for the same reason and against a sharper hazard, since these two scales do not merely differ in origin but run in opposite directions. What it is NOT: a fitment. A rating is a property of the plug's own thermal path — insulator nose length, centre-electrode conductivity, copper core, projection — and it does not change when a car model is discontinued.
Heat rating is answered with one word chosen from the heat range codes list — the same word shared across every product that uses it.
It belongs to measurement — its measurable, physical facts.
the bundle what travels with each heat rating
A heat rating is not a lone value — each statement is a self-correlating bundle, carrying its own:
asked by the kinds that answer it
1 kind answers it, each for a single value. The same question can be reused by unrelated kinds — one meaning, many homes.
asked by kinds that answer it
The same question can be reused by unrelated kinds — one meaning, many homes.
| kind | how many |
|---|---|
| spark plug | one |