The Navistar DT (Diesel Turbocharged or Diesel Turbo) engine family is a line of mid-range inline-6 diesel engines. With horsepower ratings ranging from 170 hp (130 kW) to 350 hp (260 kW), the Navistar DT engines are used primarily in medium-duty truck and bus applications such as school buses, although some versions have been developed for heavy-duty regional-haul and severe-service applications. Prior to 1986, Navistar International, then known as International Harvester Company, used the DT engine in farm and construction equipment.