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. The second item found is the fact that the results between the single oil evaluation tests by use of DSC and the actual engine performance evaluation tests agree very closely. For evaluation of oils whose performance difference is minimal, the single oil evaluation method is suitable over actual engine performance evaluation method.