Diesel fuel provides cooling of the injection system. However, the temperature of the fuel may vary considerably due to engine operating temperature. As fuel temperature increases, fuel viscosity decreases, along with the lubrication capabilities of the fuel. When the system is operated with elevated fuel temperatures, the injectors will operate at reduced internal clearances. As a result, dirt and smaller particulate material may cause injection durability concerns. Installing a fuel cooler or operating with fuel tanks above half full may also help eliminate concern. Maintaining proper fuel temperatures will help provide proper fuel injection system functioning.