What is means by sae 20w 40?

SAE 20W-40 refers to a classification of motor oil based on its viscosity, as defined by the Society of Automotive Engineers (SAE). The "20W" indicates that the oil has a viscosity rating of 20 in cold temperatures (the "W" stands for winter), allowing for better cold-start performance. The "40" indicates its viscosity at high temperatures, making it suitable for warmer operating conditions. This oil is typically used in engines that require a multi-grade oil for optimal performance across varying temperatures.