Viscosity grades in Magnum diesel oils define the oil's flow characteristics at different temperatures, which is critical for engine protection and efficiency. These grades are usually expressed as a combination of two numbers, such as 10W-40 or 5W-30. The first number (before the "W" for winter) indicates the oil's thickness in cold temperatures, affecting how easily the engine start... https://millenniumgroup.ae/understanding-viscosity-grades-in-magnum-diesel-oils/