Degradation of gear oils by oxidation or thermal breakdown, or both, can result in sludge buildup and render the oil unsuitable for further use as a lubricant.

This is the only test method that employs glassware to measure the amount of sludge produced during oxidation and thermal degradation. This test method is a modification of Test Method D2893 which measures the viscosity increase and precipitation number of the oil stressed at 95°C, but does not measure the amount of sludge formed.

This test method can be used to evaluate the oxidation/thermal stability of gear oils. However, the test results may not correlate with the performance of gear oils in field service.

1.1 This test method covers the determination of the oxidation characteristics of extreme pressure and non-extreme pressure gear oils and includes the quantitative determination of total sludge, viscosity change, and oil loss.

Note 1—While the round-robin tests used ISO VG 220 extreme pressure gear oils for developing precision data, the test method can be extended to other viscosity grades and to non-extreme pressure gear oils. Refer to Classification D2422 for viscosity grades.

1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

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.