Fitment and Product Information. Thermostatically Controlled LS Engine Oil Cooler Bypass Adapter Kit. Brandname: Derale Part Number: 35621 Description. This Billet Aluminum LS Engine Adapter features a built in 180°F Thermostat to help reduce engine wear and horse power loss. The oil thermostat allows the oil to bypass the cooler until it reaches 180°F at […]