Fuel Saving Four-Stroke Engine Oil for Motorcycles

Energy conserving performance by engine oils is required even for motorcycles from the viewpoint of environmental issues. The fuel efficiency of passenger car engine oils has been improved through lower viscosity and usage of friction modifiers. However, engine oils containing friction modifiers such as Mo compounds may not be applied to four-stroke motorcycles, because motorcycles normally have a wet clutch system inside the crankcase and such engine oils can decrease the clutch capacity. Therefore, it is important to investigate the effects of oil formulation in order to develop motorcycle engine oils, which can improve fuel efficiency and preserve clutch capacity^1)∼2). In this study, fuel efficiency of prototype oils was evaluated with a motorcycle engine motoring tester. In addition, friction coefficients of engine oils formulated with different additives such as dispersants and detergents in clutch system were evaluated with an SAE No. 2 clutch friction tester. As a result, it was found that polybutenyl succinimide borate and several detergents showed a high friction coefficient for clutches. A formulation of fuel saving 5W-30 engine oil containing Mo compounds that can cope with both fuel efficiency and clutch capacity was found.