According to the recent dieselization and the decrease in the amount of crude oil processed in Japan, the shortage of middle distillate including diesel fuels is problem. The useful methods for increasing the yield of the middle distillate are the deeper-cut and blending of cracked distillate such as light cycle oil from FCC. For the use of these methods to the diesel fuel design, effects of fuel properties such as viscosity, distillation range, cetane number on diesel performance were studied. Especially, the effects on gaseous and smoke emissions, diesel knock, startability, fuel consumption in passenger cars equipped with indirect injection engines and trucks equipped with direct injection engines were evaluated. In addition, cold performance of both cars was also investigated. One of the main conclusions of this study is that lower cetane fuels is generally associated with increased emissions and fuel consumption.