In this paper, Computational Fluid Dynamics (CFD) approach is adopted to study the combustion and emission progression in a single cylinder four stroke diesel engine, operated in both diesel and dual-fuel modes. The study of dual-fuel mode is performed by using synthesis gas (syngas) with 75:25 and 50:50 volumetric combinations of hydrogen and carbon monoxide, respectively. The modeling and meshing of the constant volume combustion chamber is carried out by using GAMBIT tool. The meshing of the combustion chamber is performed using tetrahedral elements and the k-ε turbulence model is introduced along with non-premixed combustion modeling. The modeled hemispherical-piston-top combustion chamber is then simulated in FLUENT solver across the experimental boundary conditions at 40%, 60%, 80% and 100% of full load for both diesel and dual-fuel. The results of simulation incorporate the study of maximum combustion temperature, maximum combustion velocity and H2O mole fraction subsequent to combustion. Further, the concentrations of emissions have also been investigated for both diesel and dual-fuel modes. The results of simulations show a good agreement with the corresponding experimental data. Copyright © 2010 by ASME.