A thermostat allows 90% of the oil to bypass the oil cooler until the temperature reaches 92°C (197.6°F). 10% of the oil always circulates through the cooler to prevent air pockets and shocking the system with oil that is too cold.
HEL Performance Thermostatic Oil Cooler Kit for NISSAN 370Z
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HEL Performance Thermostatic Oil Cooler Kit for TOYOTA A80 SUPRA JZA80 1993-2002