CaterpillarĀ® G3500 and G3600 series engines. Iridium Saver.
Cross reference: 7306, FB77WPCC, 301-6663.



The GI3-3 Industrial Iridium Saver spark plug reduces maintenance costs by extending work life in high compression lean burn engines. This unique design guarantees high reliability for withstanding high combustion pressure by incorporating a stress resistant monolithic resistor that adheres to the resistor glass in the high temperature furnace.

Specific details of this model include:

  • Thread Size: 18mm x 1.5
  • Reach: 20.6mm (13/16″)
  • Hex Size: 22.2mm (7/8″)
  • Gap: 0.3mm (.012″)
  • 100% Pre-Fired: All Denso spark plugs are 100% pre-fired to assure the highest quality possible.
  • Copper-Glass Seal: Bonds the center electrode and insulator together for a gas-tight seal. Maintains proper heat and excludes hot combustion gases.
  • Purified Alumina Powder Insulator: Provides exceptional dielectric strength and thermal conductivity allowing the material to stand up to extreme stress.
  • Solid terminal nut.
  • Platinum-alloy tipped fine wire ground electrode, with a platinum pad on the ground electrode and an Iridium pad without cross grooves on the center electrode.

The Denso GI3-3 Industrial Iridium Saver works in the following engine applications:

CATERPILLAR: G3500 (non B, C and E series), G3600 series

CUMMINS: Q19G, QSV81-V16, QSV91-V18

GUASCOR: FG180, FGLD180, FG240, FGLD240, FGLD360, FGLD480

GE JENBACHER: J612, J616, J620 (1995/9 – BMEP = 16 bar or less)

PERKINS: 4000 Series

SUPERIOR: 1706G2, 1712G1


AT Series: 8L-AT25GL / AT27GL (13/16″ Reach Heads), 12V-AT25GL / AT27GL (13/16″ Reach Heads)
VGF Series Inline 6: F18G, F18GL/GLD
VGF Series Inline 8: H24G, H24GL/GLD
VGF Series V-12: L36GL/GLD
VGF Series V-16: P48GL/GLD
VHP Series Inline 6: 2895GL (13/16″ Reach Heads), 3521GL (13/16″ Reach Heads)
VHP Series V-12: L5108GL (13/16″ Reach Heads), L5790GL (13/16″ Reach Heads), L7042GL (13/16″ Reach Heads)
VHP Series V-16: P5115GL, P9390GL (13/16″ Reach Heads)