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The main evaluation methods of two-stroke engine oil were standardized as the JASO (JASO: Japanese Automobile Standard Organization) method in 1993(1). After the establishment of the JASO specification, the authors executed an evaluation of various oils. As a result, it has been determined that an examination method that also evaluates the differences in demands on oil caused by regional characteristics and use conditions of the engine is necessary. Thus, the three following methods were developed. The first is a method of low-temperature detergency examination. The second is a method of low-temperature start-ability examination. The third is an exhaust port carbon blocking examination. These three examination methods are explained in full in this paper.

Two-stroke gasoline engine is lightweight, compact and has numerous advantages. However, because of its inherent engine configuration, engine oil is used as once-through system and is discarded, resulting in exhaust smoke in some occasions. In order to reduce the exhaust smoke, it is imperative to make improvement not only in engine itself but also in oil used. No standard method was available to evaluate engine smoke performance. This study was initiated to devise a simple evaluation method. In two studies reported here, evaluation of oil alone and evaluation of oil performance in actual engines are given. Following two facts were found as a result. The first item is the fact that oil can be evaluated by any actual engine performance evaluation method once the engine used and the method used are specified. The simplest and the most accurate method among the actual engine performance methods is the method to use the small two-stroke electric generator.