The article describes the results of combustion of a mixture of PCOME (purified cooking oil esters) and bioethanol in the compression ignition Perkins 1104C-44 engine. The engine was prepared for use with the classic type of fuel – diesel oil, not biofuels. That is why bioethanol was added to ester in tests so that the basic physicochemical properties of the obtained mixture were as close as possible to diesel fuel. Thanks to this, the use of such fuel in the future would not require reworking or adjusting the settings of selected elements of the engine power supply system. During this case study, the engine performance and heat release rate were analyzed. For comparison, tests were carried out while powering the engine with ester fuel, 10 and 20 per cent mixtures of bioethanol and PCOME. The speed and load characteristics for each fuel were determined. This article presents selected characteristics where the biggest differences were noticed.