Substituted N-thiomethylphenothiazines as lubricant stabilizers

A lubricant composition consisting essentially of a mineral oil or a synthetic oil or mixtures thereof and an effective stabilizing amount of a compound of the formula ##STR4## wherein R.sub.1 are independently hydrogen, alkyl of 1 to 24 carbon atoms, cycloalkyl of 5 to 7 carbon atoms or aralkyl of 7 to 9 carbon atoms;

• A is methylene and A' are independently akylene of 1 to 8 carbon atoms;
• n is 0 or 1;
• and
• R.sub.2 is alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 7 carbon atoms, said cycloalkyl substituted by alkyl of 1 to 18 carbon atoms, phenyl, phenyl substituted by alkyl, alkoxy or thioalkyl to a total carbon atom content of 7 to 30, naphthyl or naphthyl substituted by alkyl, alkoxy or thioalkyl to a total carbon atom content of 11 to 40.