K 2500 Truck 4WD V8-6.0L VIN U (1999)
has a fine wire electrode, nickel plated shell and a platinum pad across from the electrode.
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Normal service is a mixture of idling, low speed, and high speed operation.
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Occasional high speed driving is essential to good spark plug performance.
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Increased combustion heat burns away excess carbon deposits, which accumulate from frequent idling or stop-and-go driving.
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The heat resistant, insulating boot covers the spark plug terminal.
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The boot extends over a portion of the spark plug insulator.
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These boots prevent engine misfiring.
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Corona discharge is a steady blue light appearing (in darkness) around the insulator, just above the shell crimp.
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Do not mistake this for a shorted insulator.
This is visible evidence of a high-tension field.
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This has no effect on ignition system performance.
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This discharge repels dust particles.
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This leaves a clear ring on the insulator just above the shell.
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This is not evidence that combustion gases are escaping.
