Research on diesel engines has become increasingly important as engine manufacturers seek to reduce carbon dioxide emissions. There are significant advantages to using a diesel piloted natural gas engine as a DF engine. Different combustion patterns exist due to changes in mixture formation. The delay in the timing of the second pilot injection increased THC emissions (maximum 4.27g/(kW h) at low and medium loads) and reduced NOx emissions (7.64g/km) but increased and then subsequently decreased thermal efficiency value.