Patent ID: 7018958

Claim:
A method of operating a heavy duty diesel engine equipped with an aftertreatment device containing an oxidation and/or reduction catalyst, which method comprises lubricating said engine with a lubricating oil composition having a TBN of at least about 8, said composition comprising: (a) a major amount of oil of lubricating viscosity; (b) an amount of one or more dihydrocarbyl dithiophosphate metal salt introducing into said lubricating oil composition no more than 0.06 wt. % of phosphorus; (c) at least 1.2 wt. % of hindered phenol antioxidant; (d) boron, and/or a boron-containing compound or compounds in an amount providing said lubricating oil composition with at least 200 ppm by weight of boron; and (e) a minor amount of detergent.