This International Standard specifies a method to assess the resistance to shear stresses applied to mineral oils, synthetic oils and other fluids containing polymers, when passed through a specified diesel injector nozzle. The shear stability is measured by the change in viscosity of the fluid under test, brought about by the polymer degradation during stress. Under normal circumstances, this International Standard is applied to hydraulic fluids of categories HR and HV as defined in ISO 6743-4 ((1) in the Bibliography) and specified in ISO 11158 ((2) in the Bibiolgraphy), but it may also be applied to fire-resistant hydraulic fluids within categories HFA,