What energy losses are not considered when determining the efficiency of an ideal cyclic motor?

Real heat engines have a low efficiency. It does not even reach 50%. This is due to the fact that the working fluid, having received energy from the burnt fuel, cannot completely convert it into mechanical energy. Part of the internal energy of the gas is inevitably transferred to the refrigerator, dissipated in the surrounding space, and spent on work against the frictional forces of engine parts.