Patent ID: 7462583

Claim:
A method of lubricating an internal combustion engine and improving the efficiency of the emissions control system of the engine, the emissions control system being equipped with a catalyst containing exhaust gas after treatment device, the method comprising: (A) selecting a lubricating oil composition comprising: a base oil; an alkali or alkaline earth metal-containing detergent; a metal salt of one or more phosphorus-containing compounds represented by the formula wherein in formula (I), X 1 and X 2 are independently O or S, and R 1 and R 2 are independently hydrocarbyl groups, the average total number of carbon atoms per phosphorus-containing moiety being at least 10.4, wherein at least one of the R 1 and R 2 groups in one or more of the phosphorus-containing compounds contains 4 or fewer carbon atoms and up to about 40 percent of all the R 1 and R 2 groups supplied by the phosphorus-containing metal salt contain 4 or fewer carbon atoms; and an acylated nitrogen containing compound having at least about 10 aliphatic carbon atoms and a TBN of at least about 2; the lubricating oil composition being characterized by a phosphorus concentration of up to about 0.12% by weight and the substantial absence of copper; (B) adding the lubricating oil composition to the engine; (C) operating the engine; (D) generating a lean-phosphorus containing exhaust gas; and (E) contacting the catalyst in the exhaust gas after treatment device with the lean-phosphorus containing exhaust gas.