FUEL PROPERTY DETERMINATION SYSTEM FOR VEHICLE

An object of the present invention is to provide a technology with which when a gaseous fuel is supplied into a fuel tank of a vehicle with an internal combustion engine that uses gaseous fuel, properties of the supplied gaseous fuel can be determined promptly. To achieve the object, the fuel property determination system for a vehicle equipped with an internal combustion engine using gaseous fuel according to the present invention is adapted to calculate, when gaseous fuel is supplied to the fuel tank, the gas constant of the supplied gaseous fuel using a cross sectional area of a passage for delivering gaseous fuel to the fuel tank from a filler port and a change in the pressure in the fuel tank as parameters and to calculate the concentration of inert gases contained in the gaseous fuel using the gas constant as a parameter.