The Mishimoto racing thermostat for the 2015 Subaru WRX will promote greater cooling efficiency in your stock or modified FA20DIT. Once the engine is fully warmed up, the Mishimoto racing thermostat will open at a lower temperature than standard thermostats. This allows coolant to flow through the engine sooner, which reduces and maintains cooler engine temperatures. The Mishimoto WRX racing thermostat is the perfect addition to your street or track WRX and is a direct replacement for the stock thermostat. As with all our products, this thermostat includes the Mishimoto Lifetime Warranty.