NGK Laser Iridium SILFR6A Spark Plug

For the 2008-2014 WRX (EJ255) and 2004-2014 STI (EJ257), yes. NGK is the original-equipment supplier and Subaru lists this plug as genuine part 22401AA670. It ships pre-gapped to the 0.8mm the EJ255/EJ257 owner manual specifies. Always confirm against your specific year and engine before ordering.

Both are Laser Iridium heat-range-6 plugs, but the factory pre-gap differs. The SILFR6A ships at 0.8mm (0.032 in) and the SILFR6A11 ships at 1.1mm (0.044 in). The trailing 11 denotes the wider gap. The SILFR6A is the plug the EJ255/EJ257 owner manual specifies.

No. It ships pre-gapped to 0.8mm (0.032 in), the factory spec for the EJ255/EJ257. Iridium plugs have a fine center wire that is easy to damage, so the common guidance is not to re-gap them unless a specific tune calls for it.

NGK markets the SILFR6A (stock 7913) as a Long Life plug rated 80,000 to 100,000 miles, consistent with its iridium fine-wire metallurgy. Community removal-photo evidence at that interval for these Subaru applications was not located in our research, so treat the rating as a manufacturer claim.

Heat range 6 in the NGK system, the stock specification for the EJ255/EJ257. Modified or high-boost builds sometimes step one range colder to a 7, but heat range 6 is correct for a stock engine.