This is already a fourth issue of the journal Thermal Science (No. 4, 2011), dedicated to the recent research of processes in internal combustion engines. Once again I would like to point out great contribution of the Guest editor Prof. Stojan Petrović, who chose an interesting mix of papers covering a wide range of problems and processes from new thermodynamic cycles and thermodynamic optimization and CFD modeling up to new fuels, environmental impact, and especially many papers dealing with bio-fuels. After four issues in last four years dealing with processes in internal combustion engines, it is possible to make some analyses and conclusions. It is evident that large number of researchers are involved in research of the use of bio-fuels (bio-diesel, bio-ethanol, and other fuels derived from waste oils, or exotic plants). Results of testing presented in the papers published in the journal Thermal Science (and other journals in the world) contributed to the formation of a large database about behavior and effects of the bio-fuels burned (alone, or in blend with different derivatives of mineral oils) in internal combustion engines. Unfortunately, majority of the papers dealing with bio-fuels are only routine testing on standard experimental stand-up. Discussions of the results and deep insight in physical and chemical processes in volved are scarce and in most papers scientific approach is absent. Considering this situation, and keeping in mind already existing large and exhaustive database of bio-fuel be havior, and significant increase in the rating of the journal Thermal Science in last several years (current Impact factor reached a level over 0.7) has prompted the Editorial Board to recommend that possible future authors pay more attention to the comparison of the behavior of different bio-fuels and physical and chemical processes involved, rather than to further gathering of testing data, some times of very rare and exotic bio-fuels without any practical interest. From now on, our reviewing process will address special attention on originality, novelty, and scientific level of manu scripts. Therefore, we are choosing only experts in this field for the reviewers of the papers, as it can be seen from added list of reviewers engaged to review papers for this issue.