NGK Iridium One Step Colder 2309 Spark Plug Set

2015-2021 Subaru STI



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The One Step Colder Spark Plugs will promote a smoother running engine in a modified Subaru STI.


NGK Iridium Spark Plugs One Step Colder


  • Stock Number 2309
  • Heat Range: 7
  • Plug Gap: .031 
  • Sold as a set of (4)


NGK Iridium Spark Plugs One Step Colder

Once you start adding more boost, you must upgrade your spark plugs as depending on how much boost you are running, and especially what fuel type you are running will surpass the spark and heat limits of OEM spark plugs. NGK has designed this plug with the latest in iridium technology to deliver optimal spark for a smooth running engine. 

Note that this is a heat range 7 plug. A colder spark plug means that the plug has a higher tolerance for heat, and the more power and boost you add to your vehicle you will need to run a colder plug to avoid misfires, detonation, or buckling for a smooth and linear boost curve. 

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