The Mishimoto racing thermostat for the 2001+ Subaru Impreza WRX and STI will promote greater cooling efficiency throughout your engine.The Mishimoto racing thermostat will significantly lower high engine temperature produced by modified and upgraded turbo applications.Once the engine is fully warmed up the Mishimoto racing thermostat will open up at a lower temperature than standard thermostats, also allowing the coolant to flow through the engine sooner thus reducing and maintaining cooler engine temperatures.