15W40 is a multigrade engine oil classification that indicates how the oil behaves at both low and high temperatures, ensuring consistent engine protection in changing conditions. The “15W” shows the oil’s viscosity in cold weather—lower numbers mean better flow during cold starts—while the “40” represents its viscosity when the engine is fully warmed up, showing it stays thick enough... https://millenniumgroup.ae/what-does-15w40-mean/