The improvement in engine design and control techniques implies a reexamination of the cooling system. The aim of this research is to reduce fuel consumption and to increase passenger compartment thermal comfort through a better control of coolant flow rates and temperature. Preliminary experimental investigations, presented in the first part, permitted the development of a new cooling system. This system, described hereafter, is based on an electric pump and an automatic water-valve controlling the coolant flow rate and regulating the temperature at the cylinder head output. Finally are presented the vehicle tests; these confirm the results explained in the preliminary section: fuel consumption reduction, mainly due to a higher average coolant temperature, improved passenger compartment comfort through a monitored higher temperature level.