Bioethanol produced from renewable resources can be the substitute of gasoline or blended with it, gives better exhaust emissions, and has oxygen content to boost combustion. The combustion chamber liner of motorcycles’ engine need tobe lubricated with lubricants of engine oil characteristics. The unburned fuel from gasoline-bioethanol blends have a tendency to enter the oil sump. The increasing amount of bioethanol content accumulated within the oil may degrade the quality the engine oil. The aims of this study are to identify and to analyze the influence of gasoline-bioethanol blends accumulation on the characteristic of engine oils. The methodology applied in this study were adding gasoline-bioethanol blends (E40, E50, E60) into 3 types of commercial four-strokes motorcycle engine oils (SAE 5W-30, SAE 10W-40, SAE 20W-50) and analysing the effects of these addition to the engine oils characteristics by comparing the properties of each mixtures of fuel-lube blends. The engine oil properties choosed to be the studied parameters are density (ASTM D4052), kinematic viscosity (ASTM D445), flash point (ASTM D92) and four ball wear test (ASTM D 4172). The result gained from this study showed that the bioethanol content as fuel diluent resulted from unburned bioethanol decrease the quality of engine oils.