The degradation of lubricants in gasoline engines: Development of a test procedure to evaluate engine oil degradation and its consequences for rheology

Tests have been undertaken to study the effects of engine parameters and lubricant blends on oil degradation and engine components. A single cylinder spark ignition research engine was used for this work. The cam shaft was run on fully formulated oil and the crank and piston ring pack on the test oils. Samples were extracted from the sump, whilst the engine was running under controlled conditions, and rheological and chemical analysis data obtained from these samples. The methodology behind the testing and the engine set up is presented, as are results for the viscosity, sump carbonyl concentration and the end of test component condition for the four tests undertaken. Comparisons between the oil blends, engine parameters and results are discussed before conclusions are drawn and areas for further work highlighted.