15W40 refers to the viscosity grade of engine oil as defined by the SAE (Society of Automotive Engineers). The “15W” indicates the oil’s viscosity at low (winter) temperatures, meaning it flows like a 15-weight oil in cold conditions for easier engine starts. The “40” represents its viscosity at high operating temperatures, where it behaves like a thicker 40-weight oil to provide prop... https://millenniumgroup.ae/what-does-15w40-mean/