Engine oil viscosity grades indicate how thick or thin an oil is and how well it flows at different temperatures, helping ensure proper engine protection in both cold starts and high operating heat. Defined by the SAE (Society of Automotive Engineers), grades like 5W-30 or 10W-40 show two performance levels: the first number with the “W” (winter) reflects cold-temperature flow, while ... https://millenniumgroup.ae/engine-oil-viscosity-grades-explained-a-complete-guide/