A fuel is conditioned in a fuel supply system for more efficient combustion in a combustion chamber. The conditioning system includes a fuel vessel for fuel conditioning, at least one fuel dispersing nozzle mounted for discharge into the fuel vessel, at least one gas inlet port and at least one conditioned fuel outlet. A low level sensor registers a lower level of conditioned fuel in the fuel vessel. A high level sensor registers an upper level of conditioned fuel in the fuel vessel. A gas source feeds a gas to the fuel vessel, wherein the gas is dissolved in the liquid fuel for forming a liquid/gas fuel solution. A low-pressure fuel pump and a liquid fuel supply line supply liquid fuel from a fuel reservoir to the at least one dispersing nozzle of the fuel vessel at a pressure P.sub.1 higher than the gas pressure P.sub.2. A needle valve positioned downstream the fuel chamber, lowers the pressure, created in the fuel chamber by gas pressure P.sub.2, to lower level P.sub.3 downstream the needle valve. A resulting over-saturation causes gas to escape from solution. A high-pressure fuel pump feeds the homogeneous liquid into a combustion chamber at a pressure P.sub.4 that is higher than a pressure P.sub.5 in the combustion chamber at a moment of combustion. Finally, there is provided an electronic control system connected to receive a signal from the low level sensor and from the high level sensor for controlling the fuel level in the fuel chamber.