EXPLANATION
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 test method covers the determination of the oxidation characteristics of extreme pressure and nonextreme pressure gear oils, and includes the quantitative determination of total sludge, viscosity change, and oil loss. However, the test results may or may not correlate with the field service performance of the gear oils. 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 the sludge formed.
TEST SUMMARY
The oil sample is heated to a temperature of 120° C for 312 h while dry air is passed through it at a rate of 3 L/h. At the end the sample is cooled to room temperature and the apparatus is reweighed to determine the loss. Sludge is filtered through a vacuum filter. Viscosity of the filter oil is determined by Test Method D445.
TEST PRECISION
Where X is the found mean value.
The precision of oil loss has not been determined.
The bias of this test method has not been determined.