The paper realizes a comparative analysis of dynamics and fuel saving performances in different engine load and engine speed conditions. Also, it aims to identify factors that significantly influence engine performances. It aims to establish the correlation between functional parameters. There are stabilized mathematic models for engine’s functioning in dynamic regime by using system identification algorithm. Also, some static characteristics of engine operation at stationary modes are established. Values for appreciation criteria for the energy efficiency of the engine using experimental data have been defined and set. In order to solve the proposed problem experimental researches were carried out with a gasoline engine powered vehicle. Experimental data has been acquired and processed using a specialized tester to collect data from the onboard computer of the vehicle.