For 1990-2009 cars

The spark plugs are platinum tipped, tapered seat and resistor type. There are no gaskets on the spark plugs. When replacing the spark plugs, use only the type specified.

Idling, city, and highway driving are considered normal spark plug service. Occasional higher speed driving is needed for good spark plug performance. Driving at higher speeds increases combustion heat which burns away carbon or oxides which have built up from regular idling and stop-and-go city driving.

Insulated boots protect the spark plugs from heat. The boots cover the spark plug terminals and extend down over a portion of the spark plug insulators. The boots prevent spark plug flashover, which causes engine misfiring.

The corona is a steady blue light that appears around the insulator just above the shell crimp and can usually be detected only in darkness. The corona is sometimes mistaken for crossfire or a shorted insulator. The corona has no effect on engine performance.

The discharge may repel dust particles that leave a clear ring on the insulator just above the shell. This ring is not evidence that combustion gases have blown out between the shell and the insulator.