Abstract: A gasoline fuel composition comprising a major portion of gasoline and a minor portion of a mixture of dialkyl diphenylamines, effective to increase the octane number of the gasoline composition represented by the formula: ##STR1## where R and R' independently comprise one or more of butyl, pentyl, hexyl, heptyl and octyl alkyl radicals in any isomeric form is provided.

Abstract: A gasoline fuel composition comprising a major portion of gasoline and a minor portion of a diphenylamine, effective to increase the octane number of the gasoline composition, represented by the formula: ##STR1## where R and R' are independently hydrogen or C.sub.9 aliphatic hydrocarbons.

Abstract: A gasoline fuel composition comprising a major portion of gasoline and a minor portion of one or more polyaryl amines, effective to increase the octane number of the gasoline composition, represented by the formula: ##STR1## where R.sup.1 -R.sup.5 are independently hydrogen or C.sub.1 -C.sub.8 aliphatic hydrocarbons; R.sup.6 -R.sup.8 are independently hydrogen or C.sub.1 -C.sub.6 aliphatic hydrocarbons; x is between 0 and about 2, inclusive, y is between 0 and about 3, inclusive; and z is between about 1 and about 50, inclusive.

Abstract: A liquid jet fuel composition comprising:(a) a major portion of a liquid fuel; and(b) a minor effective portion of a thermal stabilizing additive prepared by(i) reacting a polyamine, an aldehyde and a phenol containing active hydrogen to form a phenol - aldehyde - amine condensate; and(ii) reacting said phenol - aldehyde - amine condensate and a succinic acid anhydride bearing a polyolefin - derived substituent containing residual unsaturation, thereby forming a phenol - aldehyde amine Mannich condensate polyamine succinimide product additive; and(iii) recovering said product additive.