Champion CT-482 spark plug erosion gauge provides an easy, accurate method of determining whether your plugs have reached their maximum wear limit. Simply regap the used plug to .016 nominal, then attempt to insert electrode assembly through the chamfered hole in the gauge, as shown. Penetration of the hole by the electrode assembly indicates plug has exceeded its recommended wear limits and should be replaced.
The CT-482 is calibrated to reject plugs after their electrodes have eroded to at least 1/2 their original thickness. Although aviation spark plugs will continue to fire past this wear point, the rate of electrode erosion will increase as a result of non-parallel gaps and reduced sparking area. This leads to intermittent misfire, increased ignition system wear, and possibly costly unscheduled maintenance.
