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 High - Temperature Thermostat This thermostat is designed as a direct - fit replacement for your aged factory unit. The Mishimoto thermostat has a higher activation temperature (205 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 higher activation temperature restricts coolant flow longer to allow a quicker engine warm - up, making this thermostat ideal for use in cold climates. As with all our products, this thermostat includes the Mishimoto Lifetime Warranty, ensuring superior product quality and craftsmanship.