The acronym “SAE” stands for the "Society of Automotive Engineers." The Society of Automotive Engineers is the governing body that oversees the standards of engine oil grades.
For over 100 years, the Society of Automotive Engineers has been classifying engine oil based on its viscosity. Viscosity is a term that describes an oil's performance at a given temperature. Engine oil with a higher viscosity rating is thicker and performs better at high temperatures. Engine oil with a lower viscosity rating is thinner and is recommended for colder climates. Modern multigrade engine oil is rated for both low and high temperatures.