EXPLANATION
The test method is designed to predict the high temperature deposit forming tendencies of an engine oil. This test method can be used to screen oil samples or as a quality assurance tool. It utilizes the thermo-oxidation engine oil simulation test (TEOST). The method is applicable over the range from 10 to 65 mg total deposits; although, operational experience has shown the test method to be applicable to engine oils having deposits over the range from 2 to 180 mg total deposit.
TEST SUMMARY
A sample of the engine oil at a temperature of 100° C that contains ferric napthenate and is in contact with nitrous oxide and moist air is pumped at a set flow rate past a tared depositor rod. The rod is resistively heated through twelve, 9.5 min temperature cycles that go from 200 to 480° C. When the twelve-cycle program is complete, the depositor rod rinsed of oil residue and dried and the gross rod mass obtained. The sample is flushed from the system and filtered through a tared filter. The mass of deposits on the rod plus the mass of deposits on the filter is the total deposit mass.
TEST PRECISION
Where X is the mean of two values.