15W40 is a multi-grade engine oil viscosity rating defined by the SAE (Society of Automotive Engineers). The "15W" indicates the oil's viscosity in cold temperatures, where "W" stands for winter, meaning it flows like a 15-weight oil during cold starts for easier engine lubrication. The "40" represents its viscosity at normal operating temperatures, ensuring it maintains proper thickn... https://millenniumgroup.ae/what-does-15w40-mean/