**Abstract**

Modern diesel engines are one of the main mobile energy sources and are characterized by a high degree of workflow completeness, design, and manufacturing technology. The chapter summarizes the authors' experience in improving diesel engines, increasing specific volume power, and reliability, ensuring a low level of environmental pollution emissions. The results of research using industry 4.0 technologies for systematization, choice of directions, and the search for rational ways to improve the efficiency of diesel engines are presented. The application of anergoexergy method for analyzing the efficiency of the working process of the engine and its systems is considered. Taking into consideration the operating conditions, technical solutions are proposed to improve the reliability of the most heat-stressed parts of high-powered engines. The possibilities for a comprehensive assessment of the fuel efficiency and environmental qualities of diesel engines have been expanded taking into account CO2 emissions when using traditional, alternative, and hybrid diesel fuel.

**Keywords:** fuel efficiency, toxic substances, power the reliability diesel engines alternative fuels, operation model, the anergo-exergy method, working processes, thermally stressed parts, the operating conditions
