Lubricating oil compositions

Abstract

A lubricating oil composition having a sulfur content of up to about 0.4 wt. % and a sulfated ash content of up to about 0.5 wt. % as determined by ASTM D874 is disclosed which comprises (a) a major amount of an oil of lubricating viscosity; (b) at least one oil-soluble or dispersed oil-stable boron-containing compound having greater than 400 ppm of boron, based upon the total mass of the composition; and (c) at least one oil-soluble or dispersed oil-stable molybdenum-containing compound having at least about 1100 ppm of molybdenum, based upon the total mass of the composition; wherein the lubricating oil composition has a ratio of sulfur to molybdenum of less than or equal to about 4:1.

1 . A lubricating oil composition having a sulfur content of up to about 0.4 wt. % and a sulfated ash content of up to about 0.5 wt. % as determined by ASTM D874 and comprising (a) a major amount of an oil of lubricating viscosity; (b) at least one oil-soluble or dispersed oil-stable boron-containing compound having greater than 400 ppm of boron, based upon the total mass of the composition; and (c) at least one oil-soluble or dispersed oil-stable molybdenum-containing compound having at least about 1100 ppm of molybdenum, based upon the total mass of the composition; wherein the lubricating oil composition has a ratio of sulfur to molybdenum of less than or equal to about 4:1. 
   
   
       2 . The lubricating oil composition of  claim 1 , wherein the oil of lubricating viscosity is comprised of a mineral base oil. 
   
   
       3 . The lubricating oil composition of  claim 1 , having at least about 500 ppm of boron. 
   
   
       4 . The lubricating oil composition of  claim 1 , having at least about 600 ppm of boron. 
   
   
       5 . The lubricating oil composition of  claim 1 , having at least about 700 ppm of boron. 
   
   
       6 . The lubricating oil composition of  claim 1 , wherein the oil-soluble or dispersed oil-stable boron-containing compound is selected from the group consisting of borated dispersant; a borated friction modifier, a dispersed alkali metal or a mixed alkali metal or an alkaline earth metal borate, a borated epoxide, a borate ester, a borated amide, a borated sulfonate, and mixtures thereof. 
   
   
       7 . The lubricating oil composition of  claim 1 , wherein the oil-soluble or dispersed oil-stable boron-containing compound is a dispersed hydrated alkali-metal borate. 
   
   
       8 . The lubricating oil composition of  claim 1 , having a ratio of sulfur to molybdenum of less than about 3:1. 
   
   
       9 . The lubricating oil composition of  claim 1 , having a ratio of sulfur to molybdenum of about0.5:1 to about 4:1. 
   
   
       10 . The lubricating oil composition of  claim 1 , having a ratio of sulfur to molybdenum of about 1:1 to about 4:1. 
   
   
       11 . The lubricating oil composition of  claim 1 , having a ratio of sulfur to molybdenum of about 1:1 to about 3:1. 
   
   
       12 . The lubricating oil composition of  claim 1 , having a ratio of sulfur to molybdenum of about 1:1 to about 2.5:1. 
   
   
       13 . The lubricating oil composition of  claim 1 , wherein the oil-soluble or dispersed oil-stable molybdenum compound is selected from the group consisting of a sulfurized or non-sulfirized molybdenum polyisobutenyl succinimide complex, molybdenum dithiocarbamate, dispersed hydrated molybdenum compound, acidic molybdenum compound or a salt thereof and mixtures thereof. 
   
   
       14 . The lubricating oil composition of  claim 1 , wherein the oil-soluble or dispersed oil-stable molybdenum compound is an oil-soluble molybdenum compound. 
   
   
       15 . The lubricating oil composition of  claim 1 , wherein the oil-soluble or dispersed oil-stable molybdenum compound is a molybdenum dithiocarbamate. 
   
   
       16 . The lubricating oil composition of  claim 1 , wherein the oil-soluble or dispersed oil-stable molybdenum compound is a sulfurized or non-sulfurized molybdenum polyisobutenyl succinimide complex. 
   
   
       17 . The lubricating oil composition of  claim 1 , having at least about 700 ppm of boron and a ratio of sulfur to molybdenum of about 1:1 to about 2.5:1. 
   
   
       18 . The lubricating oil composition of  claim 1 , wherein the sulfur is derived from a compound selected from the group consisting of an alkyl or alkenyl sulfide, polyisobutyl dithiothione, ashless dithiocarbamate and mixtures thereof. 
   
   
       19 . The lubricating oil composition of  claim 1 , wherein a major amount of the sulfur is derived from a bisdithiocarbamate compound of the Formula: 
     
       
         
         
             
             
         
       
     
     wherein R 13 , R 14 , R 15 , and R 16  are the same or different and are aliphatic hydrocarbyl groups having 1 to 13 carbon atoms and R 17  is an alkylene group having 1 to 8 carbon atoms. 
   
   
       20 . The lubricating oil composition of  claim 17 , wherein a major amount of the sulfur is derived from a methylenebis(dibutyldithiocarbamate). 
   
   
       21 . The lubricating oil composition of  claim 1 , wherein the oil-soluble or dispersed oil-stable boron-containing compound is a dispersed hydrated alkali-metal borate, the oil-soluble or dispersed oil-stable molybdenum compound is a sulfurized or non-sulfurized molybdenum polyisobutenyl succinimide complex, and the sulfur is derived from an ashless dithiocarbamate. 
   
   
       22 . The lubricating oil composition of  claim 1 , having a sulfated ash content of up to about 0.4 wt. % as determined by ASTM D874. 
   
   
       23 . The lubricating oil composition of  claim 1 , which is substantially free of phosphorus. 
   
   
       24 . The lubricating oil composition of  claim 1 , which is substantially free of zinc dialkyl dithiophosphate. 
   
   
       25 . The lubricating oil composition of  claim 1 , further comprising at least one additive selected from the group consisting of metallic detergents, ashless dispersants, friction modifiers, extreme pressure agents, viscosity index improvers and pour point depressants. 
   
   
       26 . A method of operating an internal combustion engine comprising the step of operating the internal combustion engine with a lubricating oil composition having a sulfur content of up to about 0.4 wt. % and a sulfated ash content of up to about 0.5 wt. % as determined by ASTM D874 and comprising (a) a major amount of an oil of lubricating viscosity; (b) at least one oil-soluble or dispersed oil-stable boron-containing compound having greater than 400 ppm of boron, based upon the total mass of the composition; and (c) at least one oil-soluble or dispersed oil-stable molybdenum-containing compound having at least about 1100 ppm of molybdenum, based upon the total mass of the composition; wherein the lubricating oil composition has a ratio of sulfur to molybdenum of less than or equal to about 4: 1. 
   
   
       27 . The method of  claim 26 , wherein the lubricating oil composition has at least about 600 ppm of boron. 
   
   
       28 . The method of  claim 26 , wherein the lubricating oil composition has at least about 700 ppm of boron. 
   
   
       29 . The method of  claim 26 , wherein the oil-soluble or dispersed oil-stable boron-containing compound is selected from the group consisting of borated dispersant; a borated friction modifier, a dispersed alkali metal or a mixed alkali metal or an alkaline earth metal borate, a borated epoxide, a borate ester, a borated amide, a borated sulfate and mixtures thereof. 
   
   
       30 . The method of  claim 26 , wherein the lubricating oil composition has a ratio of sulfur to molybdenum of less than about 3:1. 
   
   
       31 . The method of  claim 26 , wherein the lubricating oil composition has a ratio of sulfur to molybdenum of about 0.5:1 to about 4:1. 
   
   
       32 . The method of  claim 26 , wherein the lubricating oil composition has a ratio of sulfur to molybdenum of about 1:1 to about 4:1. 
   
   
       33 . The method of  claim 26 , wherein the lubricating oil composition has a ratio of sulfur to molybdenum of about 1:1 to about 3:1. 
   
   
       34 . The method of  claim 26 , wherein the lubricating oil composition has a ratio of sulfur to molybdenum of about 1:1 to about 2.5:1. 
   
   
       35 . The method of  claim 26 , wherein a major amount of the sulfur is derived from a bisdithiocarbamate compound of the formula: 
     
       
         
         
             
             
         
       
     
     wherein R 13 , R 14 , R 15 , and R 16  are the same or different and are aliphatic hydrocarbyl groups having 1 to 13 carbon atoms and R 17  is an alkylene group having 1 to 8 carbon atoms. 
   
   
       36 . The method of  claim 26 , wherein the oil-soluble or dispersed oil-stable boron-containing compound is a dispersed hydrated alkali-metal borate, the oil-soluble or dispersed oil-stable molybdenum compound is a sulfurized or non-sulfurized molybdenum polyisobutenyl succinimide complex, and the sulfur is derived from an ashless dithiocarbamate. 
   
   
       37 . The method of  claim 26 , wherein the lubricating oil composition has a sulfated ash content of up to about 0.4 wt. % as determined by ASTM D874. 
   
   
       38 . The method of  claim 26 , wherein the lubricating oil composition is substantially free of phosphorus. 
   
   
       39 . The method of  claim 26 , wherein the lubricating oil composition is substantially free of zinc dialkyl dithiophosphate. 
   
   
       40 . The method of  claim 26 , wherein the internal combustion engine is a diesel engine. 
   
   
       41 . The method of  claim 40 , wherein the diesel engine is equipped with at least a particulate trap. 
   
   
       42 . An internal combustion engine lubricated with the lubricating oil composition of  claim 1 . 
   
   
       43 . The internal combustion engine of  claim 42 , wherein the internal combustion engine is a diesel engine. 
   
   
       44 . The internal combustion engine of  claim 42 , wherein the internal combustion engine is a spark ignition engine.