Society of Automotive Engineers (SAE) has established a numerical code system for grading for both engine and transmission oils. All our oils have been grading by SAE according to their viscosity.
Oils can be separated into multigrade oils and monograde oils. Multigrade oils must fulfil two viscosity specifications, their viscosity grade consists of two numbers.
Currently, most automotive engine oils are multigrade oils, while oils for restricted usage, e.g. for seasonally used engines like lawn mowers, are often monograde oils. While the two numbers specify the SAE viscosity grade, the viscosity index shows the temperature related change of viscosity.