Lubricating Oil Composition

Abstract

A lubricating oil composition having a low sulfated ash content, a low P content, a low S content and a low Cl content and being favorably employable for lubricating a diesel engine operated using a hydrocarbon fuel oil having a low S content, comprises the following components a) to d) dissolved or dispersed in a base oil having a low S content: a) an ashless dispersant such as alkenyl- or alkylsuccinimide or its derivative, b) a calcium alkylsalicylate detergent having a low S content and containing an organic acid calcium salt, which is a mixture of an unsulfurized calcium alkylsalicylate detergent having a C 14 -C 18 alkyl group and an unsulfurized calcium alkylsalicylate detergent having a C 20 - C 28 alkyl group, c) a zinc phosphate anti-wear agent, and d) an oxidation inhibitor.

1 . A lubricating oil composition for lubricating an internal combustion engine which is operated by the use of a fuel oil having a sulfur content of not more than 0.005 wt. %, which comprises the following components a) to d) dissolved or dispersed in a base oil having a sulfur content of not more than 0.1 wt. % and has a sulfated ash content in a range of 0.1 to 1.1 wt. %, a phosphorus content in a range of 0.01 to 0.12 wt. %, a sulfur content in a range of 0.01 to 0.5 wt. % and a chlorine content of not more than 150 ppm:
 a) an ashless dispersant in an amount of 0.01 to 0.3 wt. % in terms of a nitrogen content, the ashless dispersant being selected from the group consisting of an alkenyl succinimide, an alkyl succinimide, or derivatives thereof;   b) a calcium alkylsalicylate detergent in an amount of 0.1 to 1 wt. % in terms of a sulfated ash content, the calcium alkylsalicylate detergent having a sulfur content of not more than 3 wt. % and a total base number in the range of 10 to 350 mg KOH/g, containing an organic acid calcium salt under the condition that the lubricating oil composition contains the organic acid calcium salt in an amount of 0.2 to 7 wt. % based on the amount of the oil composition, and comprising a mixture of an unsulfurized calcium alkylsalicylate detergent having an alkyl group having 14 to 18 carbon atoms and an unsulfurized calcium alkylsalicylate detergent having an alkyl group having 20 to 28 carbon atoms;   c) a zinc phosphate anti-wear agent in an amount of 0.01 to 0.12 wt. % in terms of a phosphorus content, the zinc phosphate being selected from the group consisting of a zinc dialkyldithiophosphate and a zinc dihydrocarbylphosphate, and   d) an oxidation inhibitor in an amount of 0.01 to 5 wt. %, the oxidation inhibitor being selected from the group consisting of an oxidation inhibiting phenol compound and an oxidation inhibiting amine compound,   wherein the sulfated ash content, phosphorus content, sulfur content, and the wt. % given in a) to d) above are values based on the amount of the lubricating oil composition.   
     
     
         2 . The lubricating oil composition of  claim 1 , wherein the calcium alkylsalicylate detergent of the component b) has a total base number in the range of 30 to 300 mg KOH/g. 
     
     
         3 . The lubricating oil composition of  claim 1 , wherein the unsulfurized calcium alkylsalicylate detergent having an alkyl group having a carbon atom number of 14 to 18 has a total base number in the range of 100 to 250 mg KOH/g. 
     
     
         4 . The lubricating oil composition of  claim 1 , wherein the unsulfurized calcium alkylsalicylate detergent having an alkyl group having 20 to 28 carbon atoms has a total base number in the range of 280 to 350 mg KOH/g. 
     
     
         5 . The lubricating oil composition of  claim 1 , wherein the calcium alkylsalicylate detergent comprises a mixture of the unsulfurized calcium alkylsalicylate detergent having an alkyl group having 14 to 18 carbon atoms and the unsulfurized calcium alkylsalicylate detergent having an alkyl group having 20 to 28 carbon atoms in a ratio of 2:8 to 8:2, in terms of a calcium content ratio. 
     
     
         6 . The lubricating oil composition of  claim 1 , wherein the calcium alkylsalicylate detergent comprises a mixture of the unsulfurized calcium alkylsalicylate detergent having an alkyl group having 14 to 18 carbon atoms and the unsulfurized calcium alkylsalicylate detergent having an alkyl group having 20 to 28 carbon atoms in a ratio of 4:6 to 8:2, in terms of a ratio of a content of the organic acid calcium salt. 
     
     
         7 . The lubricating oil composition of  claim 1 , wherein the ashless dispersant of the component a) comprises succinimide or a derivative thereof which is obtained by a reaction of a polybutenylsuccinic anhydride with a polyamine, the polybutenylsuccinic anhydride being obtained by a thermal reaction of polybutene and maleic anhydride in the absence of chlorine or a chlorine-containing compound. 
     
     
         8 . The lubricating oil composition of  claim 1 , which contains a molybdenum-containing compound in an amount of 0.01 to 5 wt. %. 
     
     
         9 . The lubricating oil composition of  claim 1 , wherein the lubricating oil composition has a total base number in the range of 1 to 17 mg KOH/g. 
     
     
         10 . The lubricating oil composition of  claim 1 , which is a multi-grade engine oil contains a viscosity index improver and is an oil of 0W5, 0W10, 0W15, 0W20, 0W30, 5W20, 5W30, 10W20, or 10W30. 
     
     
         11 . The lubricating oil composition of  claim 1 , which is employed for lubricating a diesel engine operated using a fuel oil having a sulfur content of not more than 0.005 wt. %, the diesel engine being mounted on an overland-running vehicle. 
     
     
         12 . A method for operating a diesel engine by the use of a fuel oil having a sulfur content of not more than 0.005 wt. % and a lubricating oil composition of  claim 1 , the diesel engine being mounted on an overland-running vehicle.