Fuji Racing Supercool Low Temperature High Flow Thermostat

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  • Regular price $62.00
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The Fuji Racing Supercool Thermostat has been in testing for most of 2022, now we are finally ready to release it to the public.

With the Fuji Racing Supercool thermostat in place, your engine coolant is allowed to circulate around the engine much earlier which allows overall engine temperatures to be reduced sooner than they would normally occur. Your coolant’s job is to carry heat out of the engine, take it through your radiator, and then flow it back into the engine at a reduced temperature to when it left. This entire process is controlled by the thermostat, having a thermostat open at a lower temperature than OEM allows the coolant to flow through the radiator quicker and longer.

The Fuji Racing Supercool Thermostat operating temprature is 71c. OEM Subaru opening temps for turbo models are 78c & Naturally aspirated models are 82c. The Fuji Supercool thermostat also features a larger opening than OEM to allow for more flow through the thermostat. Fuji Supercool 41mm Opening. OEM Subaru 39mm opening.

Testing was done on a 2005 WRX STi 2.1 stroker, we had a mix of daily driving & full-day track days (over 6,000 miles combined), coolant temps never went over 95c on a 30c summers day and daily driving was no different to an OEM thermostat. heaters worked as they should, coolant temperatures were stabilized and didn’t fluctuate. It had an OEM standard coolant radiator fitted, OEM cast impeller water pump, fuji supercool thermostat, Front mount intercooler & front mounted oil cooler. The coolant used was standard millers alpine antifreeze.


Suitable for the following models:

  • All Subaru EJ Engines
  • All Subaru EZ H6 Engines

If you are unsure of fitment or application then please contact us with your vehicle's chassis number.


  • 71c Supercool High Flow Thermostat
  • Seal

PLEASE NOTE: ALL PARTS ARE SUBJECT TO AVAILABILITY unless stock level indicated on product page.