Viscosity at the shear rate and temperature of this test method is thought to be representative of the condition encountered in the bearings of automotive engines in severe service.

The importance of viscosity at these conditions to engine lubrication has been addressed in many publications.⁴

1.1 This test method covers the laboratory determination of the viscosity of engine oils at 150C and 1 10 ⁶ s¹ shear rate using a tapered bearing simulator-viscometer (TBS Viscometer) equipped with a refined thermoregulator system. Older TBS units not so equipped must use Test Method D 4683-87.

1.2 The Newtonian calibration oils used to establish this test method cover the range from approximately 1.5 to 5.6 cP (mPas) at 150°C.

1.3 The non-Newtonian reference oil used to establish this test method has a viscosity of approximately 3.5 cP (mPas) at 150C and a shear rate of 1 x 10⁶ s ¹.

1.4 Applicability to petroleum products other than engine oils has not been determined in preparing this test method.

1.5 This test method uses the centipoise (cP) as the unit of viscosity. For information on the equivalent SI unit, the millipascal second (mPas) is shown in parentheses.

1.6 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.