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Engine selection for a specific type of transport vehicle, configuration and refinement of mathematical models of processes, improvement of engine construction are made based on the results of experimental research. However, in technical literature, and even the information resources of the manufacturers very limited information about the small engines can be found. In addition, the available data often contradicts each other. Goal of the arti-cle: experimental research of fuel efficiency and toxicity of exhaust gases of the small Briggs & Stratton Vanguard 18HP engine at different loads and speeds. Methodology. The engine performance parameters were evaluated on the experimental set-up of the internal combustion engines department of National Technical University "Kharkiv Polytechnic Institute". Characteristics of the engine on the modes with speeds 1800, 2400, 3000, 3600 rpm and loads from idle to maximum were obtained. As a result of experimental data processing volumetric efficiency and air/fuel ratios were determined. Total friction value of effective pressure was obtained by extrapo-lation the plot of fuel consumption versus brake out-put back to zero fuel consumption. Results. The impact of engine load and speed on the parameters of the fuel efficiency and emissions of the engine was analyzed. It is shown that the level of motoring losses in the small Briggs&Stratton Vanguard 18 HP en-gine corresponds to the motoring losses in gasoline engines with greater volume and speed. The empirical equation for determining total friction value of effective pressure in the engine was proposed. It is shown that formula proposed by V.G.Dyachenko provides satisfactory accuracy of determining total friction value of effective pressure. Originality of work consists in the proposed empirical dependence of total friction value of effective pressure on the engine speed for small engine. Рractical value is in the parameters of the small engine at operating speeds, the assessment of the applicability of the different empirical dependencies for evaluation of the motoring losses in the small engine.