Fire end Appearance
Normal life (Life in case of normal use)
A worn spark plug not only wastes fuel but also strains the whole ignition system because the expanded gap requires higher voltage. It also reduces the engine’s effi ciency, resulting in reduced fuel economy and increased exhaust emissions. Moreover, it contributes to pollution generated by exhaust gas.
Carbon fouling (Wet condition & Dry condition)
Actually, although there are various cases, from the view point of the safety factor, when the insulation resistance is 10MΩ or more, then engine can be started normally. If the insulation resistance drops to 0MΩ, not just dry fouling but mostly both dry fouling and wet fouling occur in combination.
Fouling by fuel additives
In order to raise the octane number of gasoline to suppress the knocking, MMT or ferrocene is added to the gasoline and due to this there is fouling in the plug. The plug fouled by MMT or ferrocene is diff erent from the plug fouled by carbon (carbon fouling) in that there is no self-cleaning even when the temperature of the plug rises. Moreover, since in this type of fouling, the deposits adhere strongly and cannot be cleaned completely, once this type of fouling occurs, the insulation resistance cannot be recovered.