The paper presents results of experimental study of the thermal processes under conditions of the MS-20 aviation engine oil forced convection in the annular channel with internal heating. Thermal and other problems of the aircraft piston and jet engines oil systems are disclosed, the goal is set, and the tasks of this article are provided. Brief information about the experimental setup and the working sections, the methodology for conducting experimental studies and the operating parameters are given. The paper provides graphs of primary and secondary processing of the obtained experimental materials on heat transfer in regard to the MS-20 oil at various operating parameters for pressure, pumping rate and heat flux density. It analyzes alterations in the wall temperature of the heated working tube, as well as the heat transfer coefficient of the MS-20 aviation engine oil depending on heat flux density, pressure and oil pumping rate in the annular channel. Generalizing dependences of the Nusselt number on the oil pumping rate and on the Reynolds number are shown and analyzed at various heat flux densities and pressures. It was experimentally established that at the temperature of the working section outer wall of 373 K and below, no carbon deposits was forming on it, which confirmed the theory of G.F. Bolshakov on temperature dependence of the sedimentation process in the hydrocarbon liquids. Based on this, authors of the article developed a new method for preventing sludge formation in the aviation motor oils and averting sludge appearance on the heated metal surfaces in the oil volume. Experimental study results became a launching pad for further research in heat transfer intensification to the aircraft engine oils and preventing sludge formation in the aircraft engines using the electrostatic fields. That would be published in the following articles by the authors in this journal.