79 Study on Bearing Lubricity of Two-cycle Engine Oil

Polybutene is generally formulated in two-cycle engine oil in order to prevent smoke and carbon accumulation on exhaust system in motorcycles. The higher content of polybutene in oil is said to be essential to maintain the initial performance of two-cycle engines. However, it is not so known that this polybutene deteriorates the lubricity of bearing. Therefore, we developed a method for evaluating the lubricity of bearing to verify the influence caused by two-cycle engine oils. The test was conducted to measure the temperature of the big end of connecting rod directly while running the engine. The bearing lubricity was evaluated by comparing the temperature of the big end of connecting rod of candidate oils with that of standard oil. A better two-cycle engine oil formulation was able to be led by adding this bearing lubricity test to the JASO(or ISO) standard tests.