The low-temperature, low-shear-rate viscosity of gear oils, automatic transmission fluids, torque and tractor fluids, and industrial and automotive hydraulic oils, Annex A4, are of considerable importance to the proper operation of many mechanical devices. Measurement of the viscometric properties of these oils and fluids are often used to specify their acceptability. This test method is used in a number of specifications.

This test method describes how to measure apparent viscosity directly without the errors associated with either interpolation or extrapolation of experimental data.

Note 1—Viscosity values obtained by either interpolation or extrapolation are subject to errors caused by gelation or non-Newtonian response to rotor speed, or both. Only in the case of known Newtonian oils is interpolation acceptable for the purpose of calibrating the rotor and glass cell. If such viscosity versus temperature plots are required, they can be made by the procedure outlined in Annex A1.

Note—Adapted from drawings of Brookfield Engineering Laboratories.

1.1 This test method covers the use of the Brookfield viscometer and a low-temperature bath for the determination of the low-shear-rate viscosity of lubricants. The test may operate in the viscosity range of 500 to 1 000 000 mPas (cP). The bath-controlled temperature is selected within the range of +5 to -40°C.

1.2 The test method uses the SI unit, milliPascal-second (mPas), as the unit of viscosity. (1 cP = 1 mPas).

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.