Dear readers, It passed almost two years from our last issue devoted to processes in internal combustion engines (Thermal Science, Vol. 18, No. 1, 2014). In the mean time, in 2014 and 2015 we have received almost 100 papers, and following results of the peer reviewing process (sometimes too long), subject editor Prof. Nenad Milji}, had opportunity to select 21 excellent papers coveting different topics - from injection and fuels spray processes to biodiesel use and combustion. Those papers are published in Part I: Research and modelling of the base processes in internal combustion engines. In Part II: Combustion processes of different fuels in different ambient conditions and geometries, we added to paper selection published in Part I, papers dealing with flow and combustion processes interesting for research and understanding processes in internal combustion engines. Finally, we used opportunity that in October 2015, was held the 17th International Symposium on Thermal Science and Engineering of Serbia - SIMTERM 2015, and in Part III, we added three papers presented in the Session: Energy Efficiency in Transport, of this Symposium.