SAE 5w-20 is the category of engine oils that meet 5w-20 viscosity requirements. SAE stands for Society of Automotive Engineers and they create the standard for how an oil flows based on temperature.  API (American Petroleum Institute) and ILSAC (International Lubricant Specification Advisory Committee) dictate minimum oil performance standards for use in vehicles that lubricant manufactures should follow. Products in this category meet SAE 5w-20, API SN, ILSAC GF-5 standards.