Carbon-Depositing Tendency of Heavier Motor-Oils
THIS article reports a series of tests on the carbon-depositing tendencies of motor oils, supplementary to those reported at the 1926 Annual Meeting.4 The first investigation was concerned with conditions prevailing in passenger-car engines, the results leading to the formation by the authors of a theory explaining the relationship between certain characteristics of oils and their carbon-depositing tendencies. In the second series of tests the authors controlled the various factors to values commonly found in heavy-duty engines and in their findings confirmed the theory previously set forth. A tentative explanation offered for certain facts revealed by the tests as to the carbon-depositing tendencies of motor-oils rests on the volatility, in the combustion space of the engine, of the oils used. An approximately straight-line relationship also was established between the amount of carbon deposited per liter of oil consumed and the Conradson carbon-residue test.