Engine and Laboratory Tests of Stability of Aviation Oils 370180
PURPOSE of the investigation reported in this paper was to find a suitable laboratory test method for the stability of aircraft-engine oils.
Three types of laboratory methods were chosen, and data were obtained on two of them using 22 aviation oils. The two methods were (1) heating the oil with the surface exposed to the air but without aeration, and (2) heating the oil under aerating conditions. Results were compared with engine data on the same 22 oils covering 30 hr. of operation in each case at cruising power with a Pratt & Whitney Hornet engine. Three conclusions are drawn:
Laboratory methods can be developed which will rate the stability of oils in almost any order, depending upon test conditions.
Methods involving aeration of aviation oils are much too severe and do not correlate with engine data.
Heating of aviation oils without aeration at a temperature of approximately 175 deg. cent. appears to be the most significant set of test conditions, and data obtained under these conditions correlate satisfactorily with the service porformance of the oils in aviation engines of moderate output.