Abstract: The internal combustion engines (M) of the invention are provided with a cooling water circuit, associated with a water radiator and with a lubricant oil circuit. The heat exchanger (HE) comprises an inlet and an outlet of water connected, in series, to an outlet of the water radiator, by means of a cooled water conduit and of the cooling water circuit, and to an inlet of the water radiator, by means of a return conduit and a hot water conduit; a fuel inlet nozzle and a fuel outlet nozzle, selectively connected to the fuel supply to the engine (M); and an inlet and an outlet of lubricant oil, connected to the lubricant oil circuit by means of respective oil conduits.

Abstract: The system is applied to an engine (M) having an injection system, a fuel feed line and a cooling system (CS), by means of a cooling fluid which circulates, through hot fluid ducts and cold fluid ducts, through the engine (M) and through a heat exchanger. The feed line has a first segment, connected to the injection system and provided with a first valve, to be closed when the fuel temperature is below a maximum value, and open when the fuel temperature reaches the maximum value. The feed line also has a second segment derived from the first and absorbing thermal energy from the hot fluid duct or from the combustion gases and provided with a second valve which remains open while the fuel temperature is lower than the maximum value, and which is closed when said temperature reaches the maximum value.

Abstract: The internal combustion engines (M) of the invention are provided with a cooling water circuit, associated with a water radiator and with a lubricant oil circuit. The heat exchanger (HE) comprises an inlet and an outlet of water connected, in series, to an outlet of the water radiator, by means of a cooled water conduit and of the cooling water circuit, and to an inlet of the water radiator, by means of a return conduit and a hot water conduit; a fuel inlet nozzle and a fuel outlet nozzle, selectively connected to the fuel supply to the engine (M); and an inlet and an outlet of lubricant oil, connected to the lubricant oil circuit by means of respective oil conduits.

Abstract: The system is applied to an engine (M) having an injection system (10), a fuel feed line (30) and a cooling system (CS), by means of a cooling fluid which circulates, through hot fluid ducts (61a, 61b) and cold fluid ducts (62a, 62b), through the engine (M) and through a heat exchanger (60). The feed line (30) comprises: a first segment (31), connected to the injection system (10) and provided with a first valve (33), to be closed when the fuel temperature is below a maximum value, and open when the fuel temperature reaches the maximum value; and a second segment (32) derived from the first and absorbing thermal energy from the hot fluid duct (61a, 61b) or from the combustion gases and provided with a second valve (34) which remains open while the fuel temperature is lower than the maximum value, and which is closed when said temperature reaches the maximum value.