Viscosity at the shear rate and temperature of this test method is thought to be particularly representative of bearing conditions in large medium speed reciprocating engines as well as automotive and heavy duty engines operating in this temperature regime.

The importance of viscosity under these conditions has been stressed in railroad specifications.

1.1 This test method covers the laboratory determination of the viscosity of engine oils at 100°C and 1·10⁶s^–1 using the Tapered Bearing Simulator (TBS) viscometer.

Note 1—This test method is similar to Test Method D 4683 which uses the same TBS viscometer to measure high shear viscosity at 150°C.

1.2 The Newtonian calibration oils used to establish this test method range from approximately 5 to 12 mPa·s (cP) at 100°C and either the manual or automated protocol was used by each participant in developing the precision statement. The viscosity range of the test method at this temperature is from 1 mPa·s (cP) to above 25 mPa·s (cP), depending on the model of TBS.

1.3 The non-Newtonian reference oil used to establish the shear rate of 1·10⁶s^–1 for this test method has a viscosity of approximately 10 mPa·s at 100°C.

1.4 Application to petroleum products other than engine oil has not been determined in preparing the viscometric information for this test method.

1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. This test method uses the milliPascal second (mPa·s) as the unit of viscosity. This unit is equivalent to the centiPoise (cP), which 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 to determine the applicability of regulatory limitations prior to use.