Abstract: A lubricating oil composition with enhanced deposit control capability is disclosed for engines operating under sustained high load conditions, such as natural gas engines and low-speed or medium-speed diesel engines. The composition comprises (a) a first base oil component selected from a Group I base stock, a Group II base stock, a Group III base stock, or a combination thereof, each having a kinematic viscosity at 100° C. of from 8.5 to 15 mm2/s; and (b) a second base oil component selected from a Group I base stock, a Group II base stock, a Group III base stock, or a combination thereof, each having a kinematic viscosity at 100° C. of from 4.0 to less than 8.5 mm2/s; wherein the weight ratio of the first base oil component to the second base oil component is in a range of from 1:10 to 1:1.15.

Abstract: Provided herein is a medium speed diesel engine crankcase lubricating oil composition comprising: (a) a major amount of an oil of lubricating viscosity; and (b) 0.15 to 2.0 weight percent of a silver lubricity borated fatty acid ester additive. Also provided is a method for reducing silver bearing wear and friction in medium speed diesel engines comprising lubricating said engine with said lubricating oil composition.

Abstract: Provided herein is a medium speed diesel engine crankcase lubricating oil composition comprising: (a) a major amount of an oil of lubricating viscosity; and (b) 0.15 to 2.0 weight percent of a silver lubricity borated fatty acid ester additive. Also provided is a method for reducing silver bearing wear and friction in medium speed diesel engines comprising lubricating said engine with said lubricating oil composition.