SY/T 0520-2008 "Rotational viscometer equilibrate method for the determination of crude oil viscosity" stipulates the technical requirements for the determination of crude oil viscosity by the rotational viscometer equilibrate method. The standard clarifies the instrument selection, sample preparation process, standardizes the test conditions and operation steps such as measurement temperature and Rotation speed, and gives data processing and result representation methods. It provides reliable technical specifications for accurately determining crude oil viscosity and mastering its rheological characteristics, and helps the process optimization and mass control of crude oil production, storage and transportation.