Dimethoxymethane, also known as methylal, is an oxygenated additive that contains approximately 42% oxygen content and is soluble in diesel fuel. Experiments were conducted by using the five kinds of blended fuels with different volumetric percentage of DMM in a diesel fuel. The test engine was used four stroke, single cylinder, DI diesel engine. Also, data was collected at 24 kinds of various engine speed-load conditions. The aim of this study was to examine the effects of the addition of oxygenated additive to diesel fuel on the emissions and the performance. Smoke emissions of all DMM blended fuels were reduced substantially in comparison with diesel fuel. In addition, this study showed that simultaneous reduction of NOx and smoke emissions could be achieved by oxygenated additive and EGR method that was applied to decrease smoke emissions increasing with NOx emissions reduction.