The article describes the operating algorithm of an internal combustion engine thermal preparation system, which incorporates a rapid warm-up subsystem, exhaust gas heat recovery, and a phase-change heat accumulator. It includes algorithms for the operation of the overall system as well as the specific algorithms for the rapid warm-up and heat recovery subsystems. The system’s function is presented according to the developed algorithm. The principles of interaction between the elements of the thermal preparation system are outlined. The conditions and limitations of the system’s operation are shown and justified. It is demonstrated that experimental studies using the described system algorithms confirm its operational capability. The results of experimental studies on thermal preparation processes of a stationary engine using the developed algorithm and system equipment are presented. The application of the proposed algorithms significantly reduces engine warm-up time to operating temperature, which in turn lowers fuel consumption and harmful emissions, while also increasing engine lifespan.