Abstract: Provided is a spark plug that includes a central electrode having a proximal end and a distal end and a cap having a central portion and plural projections extending radially from the central portion. The cap has a proximal side and a distal side, and the proximal side of the cap is attached to the distal end of the central electrode. The cap is electrically conductive, having a first electrical conductivity. A central portion of the cap defines a hole and has a thickness in a location of the hole, and the central electrode extends into the hole of the cap but terminates prior to the distal side of the cap. A filler material, which may have been deposited as a fusion medium, is disposed within a portion of the hole that is not occupied by the central electrode, with the filler material having a second electrical conductivity that is lower than the first electrical conductivity.