A distillate fuel composition for reducing nickel corrosion in internal combustion engine by contaminants in the motor fuel such as sulfuric acid, alkyl sulfate esters, comprising a motor fuel and a combination of at least one 2,5 dihydrocarbyldithio-1,3,4 thiadiazole of the formula ##STR1## wherein R.sub.1 and R.sub.2 are independently H or R.sub.3 S, where R.sub.3 is a hydrocarbyl group containing from 1 to 16 carbon atoms with the proviso that at least one of R.sub.1 and R.sub.2 is not hydrogen, and an adduct of benzotriazole or tolyltriazole and an amine.