Engine oil viscosity grades indicate how thick or thin an oil is and how well it flows at different temperatures. The Society of Automotive Engineers (SAE) grading system, such as 5W-30 or 10W-40, uses the number before the “W” (winter) to describe low-temperature flow, ensuring easier cold starts, while the second number represents the oil’s thickness at normal operating temperatures... https://millenniumgroup.ae/engine-oil-viscosity-grades-explained-a-complete-guide/