EFFECTS OF DILUTION ON BEARING FRICTION AND TEMPERATURES 260005

Tests made to ascertain the degree of crankcase-oil dilution beyond which it is unsafe to run an engine bearing are described and the data obtained are analyzed, the details of the apparatus used being specified. To study the effect of dilution only, new oil was used in each case and was diluted to the desired extent by adding to it the proper quantity of diluent; that is, samples of oil obtained from engine crankcases were distilled by heating, and the distillates were used to dilute the new oil. The apparatus used for distilling the crankcase oil was an ordinary glass still, which was operated in conformity with standard methods. Four lines of investigation were followed in making the tests, these being outlined.

In general, the results of the tests indicate that dilution of the oil up to 50 per cent has no bad effect upon the engine as regards increased friction and temperature of the bearings, although the dilution may be injurious from other standpoints. It appears that dilution of the oil does not affect the friction or the bearing temperature materially so long as a film of oil can be maintained between the surfaces. When this film breaks down, both friction and temperature increase. The tests indicate that the film does not break down until the oil becomes highly diluted if the pressure is low; but, when the pressure is increased, the diluted oil seems to be squeezed out from between the surfaces more easily, so that friction and temperature are higher.