Antioxidant Additive for Biodiesel Fuels

A composition comprising

• (a) a biodiesel and
• (b) an antioxidizing effective amount of a 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;
• 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-(α-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;
• wherein the aromatic amine to hindered phenol is present in a ratio of from about 1:4 to about 4:1 by weight;
• and
• (iii) at least one polyhydroxy phenol of general formula (III)
• wherein R is selected from the group consisting of H, alkyl, COOH and COOR4 wherein R4 is propyl, octyl or dodecyl.