Zero/Sports Cool Racing Thermostat (Subaru 1993+)PART# ZER ZS-0310002
The Zero/Sports Cool Thermo Thermostat Fits any 1993 and up Subaru has a valve opening setting of 160F (71C) which is 12F (7C) cooler than the stock thermostat setting. This allows the cooled water to circulate back from the radiator into the engine faster and keep the overall temperature cooler.The need for a more efficient cooling system is even more vital with today's turbocharged Subarus, such as the WRX and the STi. The factory cooling system has to work even harder now that it is being used to cool both the engine's oil and the turbocharger. This added strain on the cooling system can result in increased coolant temps leading to many negative side effects, one of the most unwanted being detonation that causes the vehicle's ECU to adjust timing, resulting in a loss of power. A hotter running motor also generally has a shorter lifespan than a cooler motor.
We gave this thermostat a test run in a 2002 WRX on a hot day and recorded full-throttle temperatures at an average of 24F cooler with the Zero/Sports thermostat (196F before, 172F after). This thermostat isn't just for modified vehicles; it can benefit even a stock car. The design of this thermostat allows it to open completely in the event of a thermostat failure, the stock thermostat will fail closed and cause the vehicle to overheat. The Zero/Sports Cool Thermo Thermostat is such a simple upgrade with substantial benefits; you can't afford not to use it.