THE stability of engine oils at high temperature, as indicated by their tendency to corrode bearing metals, can be tested in the laboratory, and results which correlate satisfactorily with engine tests can be obtained, according to these authors. But they warn that the apparatus does not eliminate the necessity for engine tests, inasmuch as there may be other factors tending to affect the correlation.
The apparatus for testing is said to save time and expense. A number of samples can be rated quickly under a variety of conditions; corrodibility of bearing metals or the corrosiveness of oils can be predicted approximately, thus reducing the number of engine tests needed. Likewise, oils can be “weeded” to leave only those worth engine testing. Uniformity of oils or bearings can be tested to enable check of subsequent samples with the initial, tested samples, while the effect of changing engine operation variables may be simulated so that the stability of oils can be indicated under these operating conditions.
Taking oils whose behavior was known in aircraft engines in test-house operation, Pratt & Whitney Aircraft has made tests with such satisfactory correlation in the relative order of their corrosiveness and tendency to sludge, that they now use the apparatus to distinguish between good and bad oils for aircraft engines in test-house service, the authors report.
The development of the apparatus and methods of test used are thoroughly covered in this paper.