The final work is conceived of the seven basic chapters related to the given theme. The first chapter presents the introductory considerations and the basic features of the fuel system on board, which is intended to give insight into the topic of work. The second chapter deals with the basic distribution of liquid fuels and the parameters of marine fuels. The third section refers to the entire process of fuel loading, the basic features of tanks for storage and fuel preparation, and the process of fuel transfer between tanks. The process of preparation and supply of fuels will be discussed in the fourth chapter, with a detailed description of the purification and preparation system. It will also handle fuel delivery to the engine. The fifth chapter refers to the entire fuel injection process, most of which explains the basic parts of the system and their working principle. The role of the moment, the direction and amount of fuel spraying, and the kind of spray of fuel are also explained. The specific Common Rail fuel injection system is explained in Chapter Six. We will mention the principle of work of the common rail system and its most important components. In the seventh or final chapter, conclusions will be drawn that are the outcome of long-term fuel use on ships.