A defective thermostat can result in engine overheating and potential internal damage. Improve the reliability of your 5.9L6.7L cooling system with a Mishimoto Dodge 5.9L6.7L Cummins Low - Temperature Thermostat This thermostat is designed as a direct - fit replacement for your aged factory unit. The Mishimoto thermostat has a lower activation temperature (180 degrees Fahrenheit) compared to the factory thermostat (190 degrees Fahrenheit for 99 - 10 and 2013 trucks and 200 degrees Fahrenheit for 10 - 12 trucks). The lower activation temperature allows coolant to flow through the engine earlier, which reduces and maintains lower engine temperatures. This thermostat is ideal for use in warmer climates or under extreme towingdriving conditions. As with all our products, this thermostat includes the Mishimoto Lifetime Warranty, ensuring superior product quality and craftsmanship.