The development of internal combustion engines is focused at solving problems like: fulfillment with increasingly stringent requirements regarding exhaust emissions and elimination of threats to the natural environment. The subject of this thesis is to assessment the impact of supplying a compression-ignition engine with hydrocarbon mixtures and to examine the impact of water on external parameters of the engine, such as smoke opacity. The tests were carried out using a innovative mixture of hydrated fusel oils, ethyl alcohol and ionic and/or non-ionic emulsifiers, from which was made of microemulsions with a water content in diesel oil of 5, 10, 15, 20 and 25%. The main tests were carried out on a 4-cylinder VW 1.9 TDI internal combustion engine at a constant engine crankshaft speed of 3000 rpm and variable load of 0, 30, 60, 90, 120, 150 and 180 Nm. The tests carried out showed a beneficial effect of the water content in the diesel oil on the reduction of the average value of smoke opacity, which systematically decreases with the increase in the percentage of water in the diesel oil.