 The article discusses the use of a mathematical model to demonstrate the synergy between hybrid electric vehicles, HEVs, which combine both internal combustion engines and electric motors. It also presents the results of road tests conducted using the model, comparing its performance against the factory control of the system. The tests showed that the model was able to increase the efficiency of the system by up to 9%, resulting in a significant reduction in fuel consumption. This article was authored by Maciej Lasowski, Wozniak Golubewski, Konrad Perjewoski, and others.