Correlation Between Vibration Level, Lubricating Oil Viscosity and Total Number Base of an Internal Combustion Engine Operated with Gasoline and Ethanol

Lubricating oils for automotive engines have been incorporating important improvements in chemical properties to increase engine performance, reduce fuel consumption and vehicular emissions indices, in addition to increasing the time interval for changing the lubricant itself. The objective of this study is to investigate the vibrational behavior of the block and crankshaft an Otto cycle internal combustion engine operated with ethanol and gasoline fuel as a function of the viscosity and total base number (TBN) of the lubricant. The study consisted of instrumenting the block and the 1st and 5th fixed bearings of the crankshaft with accelerometers to measure the engine vibration intensity and operating the engine on a bench dynamometer in a specific test cycle. Each experiment lasted 600 hours and every 50 hours a block and crankshaft engine vibration level were measured and 100ml sample of lubricating oil was collected to check viscosity and TBN chemical lubricant's properties. The results show that the block and crankshaft engine vibration level increases with the time of use of the lubricating oil and that this increase is very significant when the oil viscosity an TBN chemical properties reaches the minimum value stipulated by the manufacturer lubricating oil. Semi-synthetic and synthetic lubricating oils have similar engine protection characteristics, but synthetic oil protects the engine for a longer period of time due to less degradation of viscosity an TBN chemical properties compared to semi-synthetic. Mineral lubricating oil presented protection for a very short test period, due to the rapid degradation of chemical properties and measurements showed an average increase of 20% of vibration engine running with mineral lubricating oil in relation synthetic and semi-synthetic oils.

This research is important because it correlates the degradation of the lubricating oil with the engine vibration level and vibration problems in internal combustion engines produce premature wear on the internal components of the engine, which contributes to reduce the lifespan of the engine. This study also shows how is important to observe the correct application of automotive oils.