NOVELTY - The fuel composition comprises a fuel, which is hydrocarbons in a gas or liquid state, and a covalent ionic liquid additive comprising organic cations. The fuel is direct oxidation type fuel, which is made of methanol, ethanol, propanol, butanol, and natural gas. The organic cation is heterocyclic compound, which is made of nitrogen, oxygen, and sulfur, where the ionic liquid comprising the organic cation has structural formulae (I-IX). A Lewis acid is also provided.    USE - Fuel composition for a fuel cell (Claimed).    ADVANTAGE - The fuel composition promotes stable drive and prevents deterioration in output of the fuel in low temperature, high temperature and low humidity driving conditions by preventing freezing or dry out of a polymer electrolyte membrane.    DETAILED DESCRIPTION - The ionic liquid comprising the organic cation has structural formulae (I-IX). For formulae (I-IX),    R1,R2,R3,R4,R5,R6=alkylene radical or phenyl radical, -F, -Cl, -CF3, -SF5, CF3S-, (CF3)2CHS- or (CF3)3CS-;    X-=CF3CO2CO, CF3SO3SO, BF4SO, PF6SO, -O-(SO2R), -N-(SOR)2, -C-(SO2R)3, -BR4, -BR, PR6, -BR, N(C2F5SO2)2, N(CF3SO2)2, C(CF3SO2)2, trifluoromethanesulfonimide, trifluoro methyl sulfonamide, trifluoromethylsulfonate, AsF6, ClO4, NO3, BF4, PF6, SbF6, AlCl4, Al2Cl7Cl, AcO-, TfO- (trifluoromethanesulfonate), (CF3SO2)2N or CH3CH(OH)CO2CH(0H)CO.    An INDEPENDENT CLAIM is also included for a fuel system, which comprises an electricity generating part comprising separators and a membrane electrode assembly including an anode electrode and a cathode electrode that are oppositely directed to each other and a polymer electrolyte formed between the anode electrode and the cathode electrode, a fuel supply part, which comprises a fuel composition and supplied fuel to the electricity generating part, and an oxidizer supply part for supplying an oxidizer to the electricity generating part.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a diagram of the structure of the fuel system.    Power generator (115)    Fuel supply part (120)    Fuel tank (122)    Fuel pump (124)    Oxidizing agent supply part (130)