Fuel Economy of SI Vehicle Fueled by Ethanol/Gasoline Blends - Role of Engine Lubricant Viscosity

Ethanol is considered as a clean and sustainable alternative fuel for spark ignited engines due to its high octane number and lesser contribution towards vehicle exhaust emissions particularly CO and HC emissions. But it adversely affects the fuel economy of a vehicle. Also, it's a known fact that lower viscosity grade engine oil improves the fuel economy of a vehicle. In this paper, role of lower viscosity grade engine oil on fuel economy of vehicle running on different blends of ethanol/gasoline was explored. In light of it an experimental study was conducted initially on a High Frequency Reciprocating Rig (HFRR) to investigate the lubricity characteristics (friction coefficient and wear) of engine lubricant of different viscosity grade according to the ASTM G133/95 test method followed by a vehicle study on chassis dynamometer to study the emissions and fuel economy of a test vehicle run on gasoline and blends of ethanol/gasoline (E-5 and E-10). Lubricity characteristics studied on HFRR showed marginal difference in wear scar diameter (WSD) for lower viscosity grade engine oil as compared to higher viscosity oil. The Chassis dynamometer test results on Indian Driving Cycle (IDC) revealed that there was reduction in mass emissions when different blends of E-5 & E-10 were used and also an improvement in fuel economy of the vehicle when lower viscosity grade oil was used for E-5 & E-10 fueled vehicle.