Lubricating compositions containing reduced levels of phosphorus

A power transmission fluid containing up to about 0.015% by weight phosphorus which comprises

• (A) a major amount of an oil of lubricating viscosity,
• (B) at least one metal salt selected from the group consisting of
• (I) metal salts of the formula ##STR21## (II) metal salts M.sub.b.sup.a+ Y.sup.-.sub.a of a mixture of (1) at least one acid of the formula ##STR22## (2) at least one carboxylic acid having the formula R.sup.2 COOH wherein R.sup.2 contains from about 2 to about 40 carbon atoms and is an aliphatic or alicyclic hydrocarbon-based radical, each Y.sup.- is independently an anion of acids (1) or (2), M is a metal, a is the valence of the metal M, b is a number between 0.5 and 2, P is phosphorus, each X is independently oxygen or sulfur, and R and R.sup.1 are the same or different hydrocarbon groups of at least 3 carbon atoms bonded to the phosphorus, at least one bond being at a secondary carbon atom of R or R.sup.1, through an oxygen or sulfur atom, and
• (C) from about 0.005% to about 0.02% by weight boron as at least one acylated, nitrogen-containing compound made by reacting an aliphatic hydrocarbon substituted carboxylic acylating agent having at least about 10 carbon atoms in the aliphatic hydrocarbon substituent, simultaneously or sequentially, in any order, with at least one amino compound containing at least one ##STR23## group and a boron-containing reagent, provided further (B) the metal salt is the major source of phosphorous in the lubricating composition.