The problem of a combined air-oil cooled cylinder in an air cooled motor is discussed in this paper. This method has been selected due to unequal Thermal load on the upper cylinder part.The data of previous research on oil cooling show that in spite of local overheating, oil is neither foaming nor aging. In spite of oil viscosity, heat transfer is sufficient. With encreased load - with higher temperature of cooled surfaces, the heat transfer is increasing due to two influences: increased temperature difference and better convective conditions at lower oil viscosity.The consequence is a satisfactory self-regulating effect on the cooling system; where there is locally increased heat load, the efficiency of cooling is increased too.The experimental system is described and the results of the experiments on air cooled cylinders with oil channel are given. It is characteristic of the oil flow in the channel that it is Within the range of forced laminar and forced turbulent flow.The experimentally established function Nu=f(Re,Gr,Pr) which can be used in cases of combined cooling on the actual motor is stated.