Spark Plug Socket If working on one vehicle, you’ll need a single socket to suit your engine—typically in 5/8-inch or 13/16-inch size to use with a 3/8-inch drive socket wrench.

Chances are it’ll be on one side. This is the spark plug. Look for a fairly thick wire at the end of the spark plug. It’ll probably be connected with a metal spring clip or a friction fit.