Mag 1, qt, 15w40 diesel oil, high detergency & superior dispersancy keep engines clean & soot suspended in the oil despite longer drain intervals & increased soot loading, exceptional resistance to thermal degradation, even under the most severe operating temperatures, prevents viscosity increase & the deposit formation & wear that can result, superior anti-wear agents extend engine life despite high operating temperatures & extended service intervals, higher starting tbn provides added protection against acid build-up that can cause rust & corrosion, highly reliable performance over a wide range of temperatures, including severe cold.