Relatively low viscosity transmission fluids

Abstract

A relatively low viscosity transmission fluid composition, transmissions containing the fluids, and methods of operating motor vehicles with the fluids are described. The transmission fluid composition includes a lubricant basestock, at least one active sulfur-containing component, and at least one phosphorus-containing compound. An active sulfur atom content of the composition is greater than about 0.02 wt. %, and a ratio of active sulfur atoms to phosphorus atoms in the composition is above about 5. The composition has a viscosity at 100° C. ranging from about 4 to less than about 7 centistokes.

1 . A relatively low viscosity transmission fluid composition comprising a lubricant basestock, at least one active sulfur-containing component, and at least one phosphorus-containing compound, wherein an active sulfur atom content of the composition is greater than about 0.02 wt. %, a ratio of active sulfur atoms to phosphorus atoms in the composition is above about 5, and the composition has a viscosity at 100° C. ranging from about 4 to less than about 7 centistokes.  
     
     
         2 . The composition of  claim 1 , wherein the at least one phosphorus-containing compound comprises a boronated/phosphorylated dispersant and wherein an active sulfur atom to boron atom ratio in the composition is greater than about 15.  
     
     
         3 . The composition of  claim 1 , wherein the composition has a Brookfield viscosity of less than about 30,000 centipoise at −40° C.  
     
     
         4 . The composition of  claim 1  wherein the basestock selected from the group consisting of Group II basestocks, Group III basestocks, gas to liquid basestocks, and mixtures thereof.  
     
     
         5 . The composition of  claim 1 , further comprising an antioxidant, a friction modifier, a corrosion inhibitor, a surfactant, and an antifoam agent.  
     
     
         6 . The composition of  claim 1 , wherein the at least one phosphorus-containing compound is selected from the group consisting of phosphonates, phosphates, phosphites, phosphate salts, phosphorylated succinimides, and mixtures thereof.  
     
     
         7 . The composition of  claim 1 , wherein the composition has a viscosity index of greater than about 120.  
     
     
         8 . The composition of  claim 1 , wherein the at least one active sulfur-containing component comprises an extreme pressure agent.  
     
     
         9 . The composition of  claim 1 , wherein the at least one active sulfur-containing component comprises a thiadiazole of the formula  
       
         
           
           
               
               
           
         
       
       wherein R 1  is selected from straight and branched chain alkyl groups having from 1 to 30 carbon atoms, R 2  is selected from hydrogen and straight and branched chain alkyl groups having from 1 to 30 carbon atoms, and a and b are independently selected from integers ranging from 1 to 3.  
     
     
         10 . The composition of  claim 1 , wherein the at least one active sulfur-containing component comprises a compound selected from the group consisting of sulfonates, sulfurized olefins, sulfides, sulfates, and mixtures thereof.  
     
     
         11 . The composition of  claim 1 , comprising a fluid suitable for use in a continuously variable transmission.  
     
     
         12 . The composition of  claim 1 , comprising a fluid suitable for use in a dual clutch transmission.  
     
     
         13 . The composition of  claim 1 , comprising a fluid suitable for use in an automatic transmission.  
     
     
         14 . An additive concentrate for a transmission fluid comprising at least one active sulfur-containing component and at least one phosphorus-containing compound sufficient to provide more than about 0.02 wt. % active sulfur to a finished transmission fluid, and a ratio of active sulfur atoms to phosphorus atoms in the finished transmission fluid of greater than about 5, wherein the finished transmission fluid containing the additive concentrate has a viscosity at 100° C. ranging from about 4 to less than about 7 centistokes.  
     
     
         15 . The additive concentrate of  claim 14 , wherein the at least one phosphorus-containing compound comprises a boronated/phosphorylated dispersant.  
     
     
         16 . The additive concentrate of  claim 15 , wherein a ratio of active sulfur atoms to boron atoms in the finished transmission fluid is greater than about 15.  
     
     
         17 . The additive concentrate of  claim 14 , wherein the finished transmission fluid containing the additive concentrate has a Brookfield viscosity of less than about 30,000 centipoise at −40° C.  
     
     
         18 . The additive concentrate of  claim 14 , further comprising an antioxidant, a friction modifier, a corrosion inhibitor, a surfactant, and an antifoam agent.  
     
     
         19 . The additive concentrate of  claim 14 , wherein the at least one phosphorus-containing compound is selected from the group consisting of phosphonates, phosphates, phosphites, phosphate salts, phosphorylated succinimides, and mixtures thereof.  
     
     
         20 . The additive concentrate of  claim 14 , wherein the finished transmission fluid containing the additive concentrate has a viscosity index of greater than about 120.  
     
     
         21 . The additive concentrate of  claim 14 , wherein the at least one active sulfur-containing component comprises a thiadiazole of the formula  
       
         
           
           
               
               
           
         
       
       wherein R 1  is selected from straight and branched chain alkyl groups having from 1 to 30 carbon atoms, R 2  is selected from hydrogen and straight and branched chain alkyl groups having from 1 to 30 carbon atoms, and a and b are independently selected from integers ranging from 1 to 3.  
     
     
         22 . The additive concentrate of  claim 14 , wherein the at least one active sulfur-containing component comprises a compound selected from the group consisting of sulfonates, sulfurized olefins, sulfides, sulfates, and mixtures thereof.  
     
     
         23 . A finished transmission fluid comprising the additive concentrate of  claim 14  and a lubricant basestock selected from the group consisting of Group II basestocks, Group III basestocks, and gas to liquid basestocks.  
     
     
         24 . The finished transmission fluid of  claim 23 , comprising a fluid suitable for use in an automatic transmission.  
     
     
         25 . The finished transmission fluid of  claim 23 , comprising a fluid suitable for use in a continuously variable transmission.  
     
     
         26 . The finished transmission fluid of  claim 23 , comprising a fluid suitable for use in a dual clutch transmission.  
     
     
         27 . A method for improving fuel economy of a motor vehicle comprises the steps of: 
 providing a transmission fluid to a transmission of the motor vehicle wherein the transmission fluid comprises a lubricant basestock, at least one active sulfur-containing component, and at least one phosphorus-containing compound, wherein an active sulfur atom content of the transmission fluid is greater than about 0.02 wt. %, a ratio of sulfur atoms to phosphorus atoms in the transmission fluid is above about 5, and the transmission fluid has a viscosity at 100° C. ranging from about 4 to less than about 7 centistokes; and    operating the motor vehicle.    
     
     
         28 . The method of  claim 27 , wherein the at least one phosphorus-containing compound comprises a boronated/phosphorylated dispersant.  
     
     
         29 . The method of  claim 28 , wherein a ratio of active sulfur atoms to boron atoms in the transmission fluid is greater than about 15.  
     
     
         30 . The method of  claim 27 , wherein the transmission fluid has a Brookfield viscosity of less than about 30,000 centipoise at −40° C.  
     
     
         31 . The method of  claim 27 , wherein the transmission fluid includes an antioxidant, a friction modifier, a corrosion inhibitor, a surfactant, and an antifoam agent.  
     
     
         32 . The method of  claim 27 , wherein the at least one phosphorus-containing compound is selected from the group consisting of phosphonates, phosphates, phosphites, phosphate salts, phosphorylated succinimides, and mixtures thereof.  
     
     
         33 . The method of  claim 27 , wherein the transmission fluid has a viscosity index of greater than about 120.  
     
     
         34 . The method of  claim 27 , wherein the at least one active sulfur-containing component comprises a thiadiazole of the formula  
       
         
           
           
               
               
           
         
       
       wherein R 1  is selected from straight and branched chain alkyl groups having from 1 to 30 carbon atoms, R 2  is selected from hydrogen and straight and branched chain alkyl groups having from 1 to 30 carbon atoms, and a and b are independently selected from integers ranging from 1 to 3.  
     
     
         35 . The method of  claim 27 , wherein the at least one active sulfur-containing component comprises a compound selected from the group consisting of sulfonates, sulfurized olefins, sulfides, sulfates, and mixtures thereof.