A hybrid vehicle with an electric motor supplied by a fuel cell and a gasoline internal combustion engine operating in combination is described An on-board fuel fractioning system is provided to separate the standard gasoline fuel from the vehicle fuel tank into two fuel streams, namely, a vapour stream containing the lighter fraction of the gasoline fuel and a liquid stream containing the heavier fraction of the gasoline fuel. The vapour fuel stream is delivered to a fuel reformer upstream of the fuel cell, the fuel reformer converting the lighter hydrocarbons in the vapour fraction into hydrogen and carbon monoxide gases by means of a catalyst in the reformer. The gas mixture produced may be further separated into pure streams of hydrogen and carbon monoxide by means of a selectively permeable membrane, or further converted to produce more hydrogen by water-gas reaction while removing the carbon monoxide by selective partial oxidation. Only the hydrogen gas stream is fed to the fuel cell to combine with air to generate electricity to drive the electric motor. In a parallel process, the liquid fuel stream from the fuel fractioning system and the carbon monoxide from the fuel reformer are delivered to the internal combustion engine for normal combustion to produce power to supplement the electric motor.    USE -   As a hybrid power plant for a motor vehicle.    ADVANTAGE -   The invention uses standard gasoline fuel which is widely available. By first separating the gasoline into fuel fractions and feeding only the lighter vapour fraction to the fuel reformer for the fuel cell, the reforming process is more efficient requiring less energy and lower reforming temperature, while reducing the risk of contamination from sulphur, ash etc. within the reformer because these would stay mainly in the liquid fuel fraction. The heavier liquid fuel fraction, which is not suitable for reforming, is instead delivered to the engine for normal combustion. The invention enables the vehicle to be driven immediately from a cold start relying only on the internal combustion engine while the fuel reformer takes time to heat up and reach its reforming temperature. Under transient driving conditions, the internal combustion engine provides a faster response while the fuel reformer supplying the fuel cell adjusts to the changing gas flow and thermal conditions.