SAE engine oil viscosity classification - system developed by the Society of Automotive Engineers (SAE) to classify engine oils by viscosity grades. Oils are classified based on their measured viscosity at high temperature for single grade oils and at low and high temperatures for multi-grade oils. Multi-grades have a high viscosity index (V.I.) and therefore may fall into more than one SAE grade classification, e.g., SAE l0W-40, ("W" denotes suitability for winter, or cold weather use). Maximum cranking viscosities and pumping temperatures are defined in order to satisfy SAE low-temperature requirements. Low-temperature viscosity is measured at a different temperature for each grade. High shear viscosity is measured at 150°C under high-shear conditions that duplicate those experienced in the ring zone of an operating engine. See the SAE viscosity grade chart below.