Spark Plug Condition
Normal Plug
The normal insulator tip is gray, tan or light brown. There will be few combustion deposits. The electrodes are not burned or eroded. This indicates the proper type and heat range for the engine and the service.
NOTICE
The tip should not be white. A white insulator tip indicates overheating,
caused by use of an improper spark plug or incorrect throttle body
adjustments.
Wet Fouled Plug
The wet fouled insulator tip is black. A damp oil film covers the firing end. There may be a carbon layer over the entire nose. Generally, the electrodes are not worn. Fouling may be caused by excessive oil or by frequent short trips, especially in cold weather.