In this paper, the authors tackle the problem of energetic optimization of the cooling system of internal combustion engines (heat exchanger, water pump, air ventilator, hydraulic transport installation and thermostat) by the adjustment of fluid flows and their economic correlation. The adjustments can be primary, secondary and combined, resulting different characteristics, emphasized by numeric application. The increase of economic efficiency Ɛ_ec (indicator defined by authors), for imposed thermal efficiency Ɛ_t, leads to energetic savings due to the reduction of driving power and fuel consumption.