Lubricating Oil Composition and Method of Improving Efficiency of Emissions Control System

Abstract

The disclosed technology relates to a lubricating oil composition comprising at least one base oil and at least one overbased low molecular weight zinc dialkyldithiophosphate derived from one or more dithiophosphoric acids represented by the formula (I) and/or a metal salt thereof, wherein in formula (I), R 1 and R 2 are independently hydrocarbyl groups, the average total number of carbon atoms in R 1 and R 2 in formula (I) being in the range from 4 to 10, the metal ratio of the overbased low molecular weight zinc dialkyldithiophosphate being at least about 1.15:1, the lubricating oil composition being characterized by a phosphorus concentration of up to about 0.12% by weight. The disclosed technology also relates to a method of lubricating an internal combustion engine and improving the efficiency of the emissions control system of the engine.

1 . A lubricating oil composition comprising at least one base oil and at least one overbased low molecular weight zinc dialkyldithiophosphate derived from one or more dithiophosphoric acids represented by the formula 
       
         
           
           
               
               
           
         
       
       and/or metal salt thereof, wherein in formula (I), R 1  and R 2  are independently hydrocarbyl groups, the average total number of carbon atoms in R 1  and R 2  in formula (I) being in the range from 4 to 10, the metal ratio of the overbased low molecular weight zinc dialkyldithiophosphate being at least about 1.08:1, the lubricating oil composition being characterized by a phosphorus concentration of up to about 0.12% by weight. 
     
     
         2 . The composition of  claim 1  wherein the lubricating oil composition has a viscosity of up to about 16.3 mm 2 /sec at 100° C. 
     
     
         3 . The composition of  claim 1  wherein the lubricating oil composition has an SAE Viscosity Grade of 0W, 0W-20, 0W-30, 0W-40, 0W-50, 0W-60, 5W, 5W-20, 5W-30, 5W-40, 5W-50, 5W-60, 10W, 10W-20, 10W-30, 10W-40, 10W-50, 15W-40, 15W-50, 20W or 30W. 
     
     
         4 . The composition of  claim 1  wherein the base oil comprises mineral oil. 
     
     
         5 . The composition of  claim 1  wherein the base oil comprises a poly-alpha-olefin, an oil derived from Fischer-Tropsch synthesized hydrocarbons, or an hydroisomerized Fischer-Tropsch hydrocarbon oil or wax. 
     
     
         6 . The composition of  claim 1  wherein in formula (I), R 1  and R 2  are independently alkyl groups of 2 to about 5 carbon atoms. 
     
     
         7 . The composition of  claim 1  wherein in formula (I), R 1  and R 2  are each alkyl groups of about 4 carbon atoms. 
     
     
         8 . The composition of  claim 1  wherein the metal ratio of the overbased zinc dialkyldithiophosphate is in the range from about 1.15 to about 1.5. 
     
     
         9 . The composition of  claim 1  wherein the lubricating oil composition further comprises at least one alkali or alkaline earth metal containing detergent. 
     
     
         10 . The composition of  claim 1  wherein the lubricating oil composition further comprises at least one acylated nitrogen containing compound having at least about 30 aliphatic carbon atoms. 
     
     
         11 . The composition of  claim 9  wherein the alkali or alkaline earth metal-containing detergent comprises at least one salt of at least one organic sulfur acid, carboxylic acid, lactone, phenol, salixarate, or mixture of two or more thereof. 
     
     
         12 . The composition of  claim 9  wherein the alkali or alkaline earth metal-containing detergent comprises at least one salt of at least one salixarate. 
     
     
         13 . The composition of  claim 9  wherein the alkali or alkaline earth metal comprises sodium, lithium, calcium, or a mixture of two or more thereof. 
     
     
         14 . The composition of  claim 10  wherein the acylated nitrogen-containing compound is derived from at least one carboxylic acylating agent and at least one amino compound containing at least one —NH— group, the acylating agent being linked to the amino compound through an imido, amido, amidine or salt linkage. 
     
     
         15 . The composition of  claim 14  wherein the carboxylic acylating agent is a mono- or polycarboxylic acid or anhydride containing an aliphatic hydrocarbyl substituent of at least about 30 carbon atoms. 
     
     
         16 . The composition of  claim 14  wherein the amino compound is an alkylenepolyamine represented by the formula: 
       
         
           
           
               
               
           
         
       
       wherein U is an alkylene group of from 2 to about 10 carbon atoms; each R is independently a hydrogen atom, a hydrocarbyl group, a hydroxy-substituted hydrocarbyl group, or an amine-substituted hydrocarbyl group containing up to about 30 carbon atoms; and n is 1 to about 14. 
     
     
         17 . The composition of  claim 10  wherein the acylated nitrogen containing compound comprises at least one polyisobutene substituted succinimide. 
     
     
         18 . The composition of  claim 1  wherein the composition further comprises at least one boron-containing compound represented by the formula 
       
         
           
           
               
               
           
         
       
       wherein in Formulae XI, XII and XIII each R is independently an organic group and any two adjacent R groups may together form a cyclic group. 
     
     
         19 . The composition of  claim 1  wherein the lubricating oil composition further comprises one or more: dispersants, corrosion-inhibiting agents, antioxidants, viscosity modifiers, dispersant viscosity index modifiers, pour point depressants, friction modifiers, anti-wear agents, extreme pressure agents, fluidity modifiers, copper passivators, anti-foam agents, or a mixture of two or more thereof. 
     
     
         20 . A lubricating oil composition comprising at least one base oil, at least one overbased low molecular weight zinc dialkyldithiophosphate derived from one or more dithiophosphoric acids represented by the formula 
       
         
           
           
               
               
           
         
       
       and/or a metal salt thereof, wherein in formula (I), R 1  and R 2  are independently hydrocarbyl groups, the average total number of carbon atoms in R 1  and R 2  in formula (I) being in the range from about 6 to 10, the metal ratio of the overbased low molecular weight dialkyldithiophosphate being at least about 1.08:1, at least one alkali or alkaline earth metal detergent, the weight ratio of detergent metal to phosphorus in the lubricating oil composition being in the range from about 0.5:1 to about 10:1, and at least one nitrogen containing compound having at least about 30 aliphatic carbon atoms and a TBN of at least about 2, the weight ratio of nitrogen to phosphorus in the lubricating oil composition being in the range from about 0.3:1 to about 4:1, the lubricating oil composition being characterized by a phosphorus concentration of up to about 0.12% by weight. 
     
     
         21 . 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) lubricating the engine with a lubricating oil composition comprising at least one base oil and at least one overbased low molecular weight zinc dialkyldithiophosphate derived from one or more dithiophosphoric acids represented by the formula   
       
         
           
           
               
               
           
         
       
       and/or metal salt thereof, wherein in formula (I), R 1  and R 2  are independently hydrocarbyl groups, the average total number of carbon atoms in R 1  and R 2  in formula (I) being in the range from 4 to 10, the metal ratio of the overbased low molecular weight dialkyldithiophosphate being at least about 1.08:1, the lubricating oil composition being characterized by a phosphorus concentration of up to about 0.12% by weight;
 (B) generating a lean-phosphorus containing exhaust gas; and 
 (C) contacting the catalyst in the exhaust gas after treatment device with the lean-phosphorus containing exhaust gas.