On behalf of the Board of Polish Scientific Society of Combustion Engines and organizers of the 6th International Congress on Combustion Engines from the University of Warmia and Mazury in Olsztyn I would like to sincerely thank all the participants for actively taking part in the Congress which took place from June 22nd till June 24th 2015, in Olsztyn. I also hope that all the participants are satisfied with scientific value of Congress as well as with the accompanying events. I am convinced that Congress has well fulfilled its mission to integrate the scientific and technical engine society. I also hope that among the papers presented on different topics, each of the participants found something interesting for themselves. I would like to thank especially everyone involved in the organization of the Congress, for their hospitality, a friendly atmosphere as well as its excellent preparation. I look forward to seeing you all at the Seventh International Congress on Combustion Engines in 2017.