A synergistic mixture comprising from 1 to 99.9% by weight of compounds having structural elements (I) ##STR00001##
in which the free valencies on the oxygen atom and on the nitrogen atom may be combined to form a five-, six- or seven-membered ring and the benzene ring may also bear substituents at one or more of the free positions, and from 0.1 to 99% by weight of sulfur-containing organic compounds with antioxidant action. This synergistic mixture is suitable as a stabilizer for stabilizing inanimate organic material, especially mineral oil products and fuels, against the action of light, oxygen and heat.

A method of forming a composition comprising contacting a fuel and at least one compound of Formula I: ##STR00001##
wherein X is carbon, oxygen, or sulfur; R.sup.1 and R.sup.2 each independently are hydrogen, a C.sub.1 to C.sub.20 alkyl, or a C.sub.6 to C.sub.10 aryl; R.sup.3 and R.sup.3 each independently are hydrogen or a C.sub.1 to C.sub.4 alkyl; R.sup.4 and R.sup.4 each independently are hydrogen, a C.sub.1 to C.sub.4 alkyl, a C.sub.4 to C.sub.10 cycloalkyl, or a C.sub.6 to C.sub.10 aryl; R.sup.5 and R.sup.5 each independently are a C.sub.4 to C.sub.10 alkyl; R.sup.6 and R.sup.6 each independently are hydrogen or a C.sub.1 to C.sub.6 alkyl; and R.sup.7 and R.sup.7 each independently are hydrogen or C.sub.1 to C.sub.4 alkyl; and wherein the compound of Formula I when subjected to GC-MS using electron ionization at greater than 70 eV produces at least one ion having a mass-to-charge ratio of 300 to 600.

A synergistic mixture comprising from 1 to 99.9% by weight of compounds having structural elements (I) ##STR00001##
in which the free valencies on the oxygen atom and on the nitrogen atom may be combined to form a five-, six- or seven-membered ring and the benzene ring may also bear substituents at one or more of the free positions, and from 0.1 to 99% by weight of sulfur-containing organic compounds with antioxidant action. This synergistic mixture is suitable as a stabilizer for stabilizing inanimate organic material, especially mineral oil products and fuels, against the action of light, oxygen and heat.