In order to improve the performance and pollution of 16RK215 heavy duty diesel engine, numerical simulation of methane-diesel combustion was performed with method of reactivity controlled compression ignition. In the first phase, the combustion simulation is performed with 100% diesel fuel, after validation, by advancing injection timing, increase or decrease of power and pollutants analyzed. In the second phase, dual fuel combustion simulations are performed. With the aim of maximizing the use of methane gas as a cheap and clean fuel, at initial condition methane gas selected as 80% of input fuel and the remaining 20%, diesel fuel defined. Compared to diesel-only simulations, the results power reduction by 20%, thermal efficiency increases by 2% and carbon monoxide emissions are reduced by up to 50%. In the third phase, with the aim of compensating reduced power and improving the pollutants in dual fuel mode, first the effect of reducing the methane to diesel ratio is investigated, then the effect of compression ratio, injection timing and EGR discussed. The results show that the use of 70% methane and 30% combustion is more complete and the thermal efficiency increases by 5.2%. advancing injection timing increases power and reduces carbon monoxide and nitrogen oxides, 1.2 and 5.1 g/kwh, respectively. Increasing engine compression ratio leads to complete combustion, which increases the local temperature and nitrogen oxide pollutants by 5%. Manuscript profile