Development of Specially Formulated 4-Stroke Engine Oil for Motorcycles

The energy conserving by engine oils has been required from the viewpoint of the environmental issue. The fuel consumption efficiency of passenger car engine oils has been improved by adding friction modifiers. However, engine oils containing friction modifiers can cause reduction of the clutch capacity for motorcycle engines. ^1)∼2) The higher detergency is occasionally required for motorcycle engines compared with passenger car engines. Therefore, it is important that specially formulated 4-stroke engine oils, which satisfy those requirements, are developed for motorcycles. The clutch capacity of commercially available engine oils for passenger cars was evaluated according to the standard of JASO T904-98. As a result, some engine oils, which have a low clutch friction coefficient, were found. In order to develop a motorcycle engine oil, a basic additive system which has excellent detergency and oxidation stability was selected by evaluating with laboratory tests. Furthermore, the influence of additives on the clutch capacity was investigated with a laboratory test. Several additives, which increase a clutch friction coefficient, were found. A specially formulated motorcycle engine oil of 10W-30 was developed by adding one of them into the basic additive system. It was confirmed with JASO T904-98 and engine tests that it has high clutch capacity, excellent detergency and high fuel efficiency.