In the presented research, the authors dealt with the specific properties of the combustion process of dimethyl ether (DME) in a combustion car (Volkswagen Golf IV) engine AJM 1.9 TDI PDE made by Volkswagen factory. Dimethyl ether is an alternative fuel produced most often from natural gas, which can be used in compression ignition engines as a single fuel or co-burned with diesel oil. This work describes the impacts of using exhaust gas recirculation system and various diesel to DME substitution ratios from 0% to approximately 25% (on an energy basis), on the combustion process in a dual-fuel diesel engine. The engine has been modified so that DME fuel is introduced into the intake manifold just before the intake valves. The diesel fuel supply system, operation algorithms of the engine electronic control unit and other engine elements were left unchanged as it was built by the manufacturer.