The combustion and emission characteristics of a compression ignition engine fuelled with Diesel-dimethoxy methane (DMM) blends were investigated. The results showed that the initial combustion duration experienced a slight variation with the increase of DMM fraction in the fuel blends, while the rapid combustion duration and the total combustion duration decreased with the increase of DMM fraction in the fuel blends, and the crank angle of the centre of heat release curve moved closer to the top dead center. This would be due to the increase in the amount of combustible mixture for the initial premixed combustion phase because of the fast evaporation of DMM and the promotion of the subsequent diffusive combustion phase resulting from the oxygen enrichment. The maximum cylinder pressure and the maximum mean cylinder temperature showed a slight increase with the increase of DMM addition. The enrichment of oxygen by injecting the oxygenate fuel is responsible for the combustion improvement. The maximum rate of pressure rise and the maximum rate of heat release will increase with the increase of the DMM fraction in the fuel blend, and this would also be due to the increase in the amount of combustible mixture for the premixed combustion phase fuelled with the Diesel-DMM blends. A remarkable reduction in the exhaust CO and smoke can be achieved when operating on the Diesel-DMM blend. Flat NOx-smoke curves are presented when operating on the Diesel-DMM fuel blends, and a simultaneous reduction in both NO, and smoke can be realised at large DMM additions. Thermal efficiency and NO, give the highest value at 2% oxygen mass fraction (or 5% DMM volume fraction) for the combustion of Diesel-DMM blends. (c) 2005 Elsevier Ltd. All rights reserved.