This system is established by the Society of Automotive Engineers (SAE) and it is representing viscosity of the engine oil. In general, the viscosity grading includes 0-60, (from low to high viscosity). Using ‘SAE5W40’ as an example, ‘5W’ represents the viscosity under cold-start is ‘5’, ‘W’ represents ‘Winter’, and ‘40’ represents the viscosity at high temperature (100-150C).

In general, the lower the viscosity, the greater the mobility of the oil to start the engine; and the higher the viscosity helps to lubricate the components. Drivers may choose the engine oil according to the driving environment and performance. Regular replacement of the engine oil can helps to maintain the car in best performance.