OXIDATION STABILITY OF OILS BY THIN FILM OXYGEN UPTAKE (TFOUT): ASTM D4742
EXPLANATION
This test method is used to evaluate oxidation stability of lubricating base oils with additives in the presence of chemistries similar to those found in gasoline engine service. Test results for some ASTM reference oils have been found to correlate with sequence IIID engine test results; however, this test is not a substitute for the engine testing of an engine oil in established engine tests. This test method can be used for engine oils with viscosity in the range from 4 cSt to 21 cSt at 100° C including the re-refined oils.
TEST SUMMARY
The oil is mixed in a glass container with three other liquids that are used to simulate engine conditions: an oxidized/nitrated fuel component, a mixture of soluble metal napthenates (lead, copper, iron, manganese, and silicon), and distilled water. The container with the oil mixture is placed in a high pressure reactor equipped with a pressure gage. The reactor is sealed and charged with oxygen to a pressure of 620 kPa, and placed in an oil bath at 160° C at an angle of 30° from the horizontal. The reactor is rotated axially at a speed of 100 r/min forming a thin film of oil within the glass container resulting in a relatively large oil-oxygen contact area. The pressure of the reactor is continuously recorded from the beginning of the test. The test is terminated when a rapid decrease of the reactor pressure is observed. The time period between these two events is called the oxidation induction time and is used as a measure of the relative oil oxidation stability.
TEST PRECISION
Repeatability: 0.10(X + 5min)
Reproducibility: 0.22(X + 5min)
Where X is the mean of the results.
A bias statement is now being developed.
