Reassessment of engine oil periodicity in commercial vehicles (c)

Thermo-oxidative stresses deteriorate physical and chemical properties of o il in the lubrication systems of combustion engines and render it ineffecti ve over a period of time. It leads not only to excessive wear and corrosion but may also cause catastrophic failure of lubricated components. A realis tic reassessment of oil periodicity calls for evaluation of oil under actua l field application of the system. In this paper, oil change periodicity of SAE 10W 30 engine oil for two commercial vehicles is examined. Conventiona l tests such as viscosity, total acid number (TAN), water content, flash po int, ail insolubles, atomic absorption spectroscopy (AAS), and ferrography, and less conventional techniques such as sealed pan differential scanning calorimetry (SPDSC) in combination with differential infrared (DIR) spectro scopy and thin layer chromatography (TLC) have been employed for estimating remaining useful life of engine oil of the two vehicles. Good correlations were observed in the properties studied including depletion of multifuncti onal additive ZDDP A map was also constructed to indicate safe and unsafe z ones for kilometerage run. In addition, the results indicated that the TLC technique has potential to be a good supporting technique for additive depl etion assessment. The results indicated that both oil systems showed good h ealth beyond the recommended periodicity level (PR) i.e. 10,000 Kms. Howeve r; engine wear debris analysis calls for more frequent oil sampling in the vicinity of PR and newly recommended periodicity level (PN) for realistic r eassessment of periodicity.