Diesel engines are the powerplant of most commercial trucks and construction equipment, and for good reason. These engines deliver the required horsepower and necessary torque to move the heavy loads in the most extreme conditions. The procedure we use to determine service intervals is based on the type of application the truck or equipment is being used for and the number of annual miles or hours the engine will be operating. Since the life expectancy of an engine is directly related to the quality and frequency of the oil and filter changes, we only use the best synthetic oil and filters. Additionally, diesel engines rely on clean filtered fuel to fire in the combustion chamber through the fine tip nozzles of a fuel injector. We replace the fuel filter or multiple filters during every PM service. Lastly, we replace the engine air filter during every PM service for the simple reason that engines need to breath clean air without restriction to avoid any incorrect air/fuel ratios.