The kalilnoe number of a spark plug is an indicator of its ability to resist to thermal loadings. That candles worked reliably, they should reach quickly after engine start self-cleaning temperatures approximately 400 S.Esli are not present, on the thermal case of an insulator the deposit can be formed. At full loading on the engine the temperature of heating of an insulator should not exceed 800 S.Na all engines operating conditions for spark plugs are not identical, therefore the choice correct калильного numbers for the concrete engine depends on quantity of heat, received and taken away at combustion. If, for example, you use a candle with smaller калильным number the insulator will overheat also it can lead калильному to ignition, and even to destroy the engine. If, on the contrary, you choose a candle with high калильным number, it will not reach self-cleaning temperature — and the insulator will become soiled.