In order to check your viscosity cup's calibration or to certify it for ISO purposes, it is imperative that you use viscosity standards.

Standard oils have a specific drain time, dependent on the viscosity cup type (Ford, Shell, Zahn, etc), and the orifice or cup number used.

To check the viscosity cup, simply use the standard viscosity oils in place of your liquid and measure the drain time.

(½ Litre/1 Pint).