Engine oil viscosity grades explained

Engine oil viscosity grades describe the oil’s resistance to flow and its ability to protect the engine across different temperatures, as defined by SAE standards. The first number in a multi-grade oil, followed by “W” (such as 10W or 5W), indicates how easily the oil flows during cold starts, helping reduce startup wear. The second number (for example, 30 or 40) represents the oil’s thickness at normal operating temperatures, ensuring a stable lubricating film under heat and load. Selecting the correct viscosity grade is essential for maintaining proper lubrication, preventing excessive friction, and supporting overall engine performance and longevity.