Soot control for diesel engine lubricants

Abstract

The present invention is directed to a method for controlling soot induced viscosity increase in diesel engines, by using as the diesel engine lubricant an oil formulation comprising a base oil containing about 10 to 80 wt % GTL base stock and/or base oil and/or hydrodewaxed or hydroisomerized/catalytic (or solvent) dewaxed base stock and/or base oil in combination with 20 to 90 wt % conventional Group I petroleum derived base oil, said base oil being further combined with a polymeric viscosity modifier, and to the lubricating oil which effects such control over soot induced viscosity increase.

1 . A method for controlling the soot induced viscosity increase of conventional/mineral oil derived base stock or base oil lubricating oils used in diesel engines during use by adding to the lubricating oil about 10 to 80 wt % of a GTL base stock and/or base oil and/or hydrodewaxed or hydroisomerized/catalytic (or solvent) dewaxed base stock or base oil, based on the weight of the total base oil. 
   
   
       2 . A method for controlling the soot induced viscosity increase of lubricating oils used in diesel engines during use by employing as the diesel engine lubricating oil an oil formulation comprising a base stock or base oil containing about 10 to 80 wt % of a GTL base stock and/or base oil and/or hydrodewaxed or hydroisomerized/catalytic (or solvent) dewaxed base stock and/or base oil in combination with about 90 to 20 wt % of a conventional petroleum/mineral oil derived base stock, based on the weight of the total base oil. 
   
   
       3 . The method of  claim 1  or  2  wherein the amount of GTL base stock and/or base oil and/or hydrodewaxed or hydroisomerized/catalytic (or solvent) dewaxed base stock and/or base oil is in the range of about 10 to 70 wt % based on the weight of the total base oil. 
   
   
       4 . The method of  claim 1  or  2  wherein the conventional petroleum/mineral oil derived base stock is a Group I and/or Group II base stock. 
   
   
       5 . The method of  claim 4  wherein the conventional petroleum/mineral oil derived base stock is a Group I base stock. 
   
   
       6 . The method of  claim 1  or  2  wherein the GTL base stock and/or base oil and/or hydrodewaxed or hydroisomerized/catalytic (or solvent) dewaxed base stock and/or base oil has a kinematic viscosity at 100° C. in the range of about 2 to 50 mm 2 /s. 
   
   
       7 . The method of  claim 1  or  2  wherein the GTL base stock and/or base oil and/or hydrodewaxed or hydroisomerized/catalytic (or solvent) dewaxed base stock and/or base oil has a kinematic viscosity at 100° C. in the range of about 3 to 40 mm 2 /s. 
   
   
       8 . The method of  claim 1  or  2  wherein the GTL base stock and/or base oil and/or hydrodewaxed or hydroisomerized/catalytic (or solvent) dewaxed base stock and/or base oil has a kinematic viscosity at 100° C. in the range of about 3.5 to 30 mm 2 /s. 
   
   
       9 . The method of  claim 2  wherein the conventional petroleum/mineral oil derived base stock has a kinematic viscosity at 100° C. in the range of about 2 to 20 mm 2 /s. 
   
   
       10 . The method of  claim 4  wherein the conventional petroleum/mineral oil derived base stock has a kinematic viscosity at 100° C. in the range of about 4 to 10 mm 2 /s. 
   
   
       11 . The method of  claim 5  wherein the conventional petroleum/mineral oil derived base stock has a kinematic viscosity at 100° C. in the range of about 4 to 8 mm 2 /s. 
   
   
       12 . The method of  claim 1  or  2  wherein the GTL base stock and/or base oil and/or hydrodewaxed or hydroisomerized/catalytic (or solvent) dewaxed base stock and/or base oil has a kinematic viscosity at 100° C. in the range of about 3.5 to 30 mm 2 /s and the conventional petroleum/mineral oil derived stock is a Group I and/or Group II stock which has a kinematic viscosity at 100° C. in the range of about 4 to 8 mm 2 /s. 
   
   
       13 . A diesel engine lubricating oil formulation resistant to soot induced viscosity increase during use comprising a base oil containing about 10 to 80 wt % GTL base stock and/or base oil and/or hydrodewaxed or hydroisomerized/catalytic (or solvent) dewaxed base stock and/or base oil, about 90 to 20 wt % of a conventional petroleum/mineral oil derived base oil, based on the weight of the total base oil and about 1 to 25 wt % on an as received basis of a polymeric viscosity modifying additive, based on the total weight of the lubricating oil formulation. 
   
   
       14 . The diesel engine lubricating oil formulation of  claim 13  wherein the GTL base stock and/or base oil and/or hydrodewaxed or hydroisomerized/catalytic (or solvent) dewaxed base stock and/or base oil comprises about 10 to 70 wt % of the total base oil. 
   
   
       15 . The diesel engine lubricating oil formulation of  claim 13  wherein the GTL base stock and/or base oil and/or hydrodewaxed or hydroisomerized/catalytic (or solvent) dewaxed base stock and/or base oil comprises about 10 to 60 wt % of the total base oil. 
   
   
       16 . The diesel engine lubricating oil formulation of  claim 13 ,  14  or  15  wherein the conventional petroleum/mineral oil derived base oil is a Group I and/or Group II base oil. 
   
   
       17 . The diesel engine lubricating oil formulation of  claim 16  wherein the base oil is a Group I base oil. 
   
   
       18 . The diesel engine lubricating oil formulation of  claim 13 ,  14  or  15  wherein the polymeric viscosity modifying additive is present in an amount in the range of about 5 to 25 wt % on an as received base, based on the total weight of the lubricating oil formulation.