In the global fuel economy, new challenges concerning the use of alternative (vegetable) fuels in the internal combustion engines are starting to arise. The important issue is to meet the new limits on four main pollutant emissions from a diesel engines: CO (carbon monoxide), NOx (nitrogen oxides), HC (hydrocarbons) and PM (particulate matter). The design of a modern engine must be characterized by high efficiency, its dynamics of movement and durability. Dynamic development of plant fuels is forced by the new strategy of the global fight against the global warming. For these reasons, it is necessary to do research concerning the effects of the use of biofuels, including methyl esters, higher fatty acids of rapeseed oil for self- ignition engines. The current tests must concern the engines equipped with the latest Common Rail fuel injection systems. In the publication, the above-mentioned issues have been analyzed, and the results of tests of the basic injection process parameters have been presented. The AVL5402 engine was fueled with mixtures of diesel oil with RME ester of rapeseed oil produced by ORLEN Południe S.A. in Trzebinia. The impact of the fuel (v/v) RME content in the mixture with diesel oil on the injection process parameters such as: initial velocity of the injected fuel, critical speed of secondary fuel breakup, critical droplet diameter, microstructure of the fuel stream, droplet Sauter mean diameter, vertical angle of the fuel stream, have been justified. The impact of the fuel (v/v) RME content in the mixture with diesel oil on the above-mentioned parameters has been proved. During the tests, the engine worked on the load characteristics.