NGK Iridium One Step Colder 2309 Spark Plug Set
NGK Iridium One Step Colder 2309 Spark Plug Set

NGK Iridium One Step Colder 2309 Spark Plug Set

2006-2014 Subaru WRX / 2004+ Subaru STI

Was: $349.60
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The One Step Colder Spark Plugs will promote a smoother running engine in a modified Subaru STI.
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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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1 customer review

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  1. Cylinder 3 spark plug casing cracked and caused a misfire

    By Did not work well in 2018 STI August 24, 2022

    Sadly I cannot recommend these plugs. I purchased them and the car ran oddly, I went to do a few pulls before race day and sadly cylinder 3 was misfiring. I tracked it down to these NGK plugs. I pulled out the plug in cly 3 and the porcelain was cracked. I ordered the oem NGK plugs from Subaru and then threw these ones out. Did an install and no issues, idle is also back to normal. I could have got a bad batch. $20 for 4 vs $70 for 4, I'll always use NGK, but not these plugs.

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