NOVELTY - A composition comprises: a) a biodiesel and b) antioxidizing mixture of i) at least one aromatic diamine selected from e.g. N,N'-di-isopropyl-p-phenylenediamine, N,N'-di-sec-butyl-p-phenylenediamine or N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine; ii) at least one hindered phenol selected from e.g. 2,6-di-tertbutylphenol, 4-methyl-2,6-di-tert-butylphenol, 2,4,6-tri-tertbutylphenol, 2-tert-butylphenol, or 2,6-diisopropylphenol, where the aromatic amine to hindered phenol is present in a ratio of 1:4-4:1 by weight; and iii) at least one polyhydroxy phenol.    USE - In biodiesel fuel; for inhibiting oxidation of biodiesel.    ADVANTAGE - The composition provides excellent characteristics for biodiesel fuel composition; effectively stabilizes biodiesel fuels against oxidation degradation and deposit formation; provides synergistic antioxidant activity in biodiesel fuel. The composition as antioxidants in fuels stored for long periods act in a stabilizing capacity, i.e. prevents insoluble oxidation products from forming and settling out, as such, fuels remain clear and bright, or stable; as antioxidants added at the point of manufacture, at elevated temperatures, can act as scavengers preventing thermal induced free radical formation.    DETAILED DESCRIPTION - A composition comprises: a) a biodiesel and b) antioxidizing mixture of i) at least one aromatic diamine selected from N,N'-di-isopropyl-p-phenylenediamine; N,N'-di-sec-butyl-p-phenylenediamine; N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine; N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine; N,N'-bis(1-methylheptyl)-p-phenylenediamine; N,N'-dicyclohexyl-p-phenylenediamine; and N,N'-dioctyl-p-phenylenediamine; ii) at least one hindered phenol selected from 2,6-di-tertbutylphenol; 4-methyl-2,6-di-tert-butylphenol; 2,4,6-tri-tertbutylphenol; 2-tert-butylphenol; 2,6-diisopropylphenol; 2-methyl-6-tert-butylphenol; 2,4-dimethyl-6-tert-butylphenol; 4-ethyl-2,6-di-tertbutylphenol; 2-methyl-6-styrylphenol; 2,6-di-styryl-4-nonylphenol; 2-tert-butyl-4,6-dimethylphenol; 2,6-di-tert-butyl-4-ethylphenol; 2,6-di-tert-butyl-4-n-butylphenol; 2,6-di-tert-butyl-4-iso-butylphenol; 2,6-di-cyclopentyl-4-methylphenol; 2-( alpha -methylcyclohexyl)-4,6-dimethylphenol; 2,6-di-octadecyl-4-methylphenol; 2,4,6-tri-cyclohexylphenol; 2,6-di-tert-butyl-4-methoxymethylphenol; 3-tert butyl-4-hydroxyanisole; and o-tert-butylphenol, where the aromatic amine to hindered phenol is present in a ratio of 1:4-4:1 by weight; and iii) at least one polyhydroxy phenol of formula (I).    R=H, alkyl, COOH or COOR4;    R4=propyl, octyl or dodecyl.