A REVIEW OF DEGRADATION PROCESS ON COMPRESSED NATURAL GAS AND DIESEL ENGINES LUBRICANT OILS

In this study, a representative sample of urban buses, powered with CNG and diesel engine technologies and working on urban duty operation, have been studied in order to evaluate engine oil evolution of degradation. Main parameters evaluated have been related with oil degradation: oxidation, nitration, viscosity, Antioxidant additives depletion, antiwear, TAN, TBN and RUL Number. Results obtained have shown higher degradation rates for oils used on CNG engines than diesel engine. CNG engines studied showed a high thermal and mechanical stress, and lower oil sump volume. Experience with FUR technique on degradation study allowed to define optimal spectral ranges to quantify the changes of oxidation, nitration and fuel dilution problem in MCIA.