Lubricating oil compositions with oxidative stability in diesel engines

Abstract

A method for improving oxidative stability of a lubricating oil in a diesel engine by using as the lubricating oil a formulated oil. The formulated oil has a composition including a lubricating oil base stock as a major component, and at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock as minor components. The at least one aminic antioxidant is present in an amount from 0.1 to 2.5 wt. %, the at least one phenolic antioxidant is present in an amount from 0.5 to 5 wt. %, and the at least one Group V base stock is present in amount from 1 to 20 wt. %. Oxidative stability is improved in a diesel engine lubricated with the lubricating oil, as compared to oxidative stability achieved in a diesel engine lubricated with a lubricating oil containing a minor component other than specified antioxidants and Group V base stock.

1 . A method for improving oxidative stability of a lubricating oil in a diesel engine by using as the lubricating oil a formulated oil, said formulated oil having a composition comprising a lubricating oil base stock as a major component; and at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock, as minor components; wherein the lubricating oil base stock is present in an amount from about 1 to about 95 weight percent, based on the total weight of the lubricating oil; wherein the at least one aminic antioxidant is present in an amount from about 0.1 to about 2.5 weight percent, the at least one phenolic antioxidant is present in an amount from about 0.5 to about 5 weight percent, and the at least one Group V base stock is present in an amount from about 1 to about 20 weight percent, all based on the total weight of the lubricating oil; and wherein oxidative stability is improved in a diesel engine lubricated with the lubricating oil, as compared to oxidative stability achieved in a diesel engine lubricated with a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock, as measured by a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048. 
     
     
         2 . The method of  claim 1  wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the number of hours to break as measured by Fourier-transform infrared spectroscopy (FT-IR) or by kinematic viscosity at 40° C. (KV40) of said lubricating oil, is greater than about 252 hours as compared to the number of hours to break as measured by FT-IR or KV40 of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock. 
     
     
         3 . The method of  claim 1  wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the relative kinematic viscosity at 40° C. (KV40) increase from 300 to 360 hours of said lubricating oil, is less than about 100 percent increase as compared to the relative kinematic viscosity at 40° C. (KV40) increase from 300 to 360 hours of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock. 
     
     
         4 . The method of  claim 1  wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the amount of lead present in end of test used oil of said lubricating oil, is less than about 100 ppm as compared to the amount of lead present in end of test used oil of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock. 
     
     
         5 . The method of  claim 1  wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the FTIR oxidation peak height at end of test, is less than about 175 Abs/cm as compared to the FTIR oxidation peak height at end of test of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock. 
     
     
         6 . The method of  claim 1  wherein the at least one phenolic antioxidant comprises a substituted phenol that contains at least one alkyl substituent group; a sterically hindered phenol that contains an alkyl group ortho to the hydroxyl group, or two alkyl groups ortho to the hydroxyl group that occupy the 2-position and 6-position of the phenolic ring, or a mixture thereof; or an alkylene or alkylidene coupled sterically hindered phenol oligomer. 
     
     
         7 . The method of  claim 1  wherein the at least one phenolic antioxidant comprises a substituted phenol containing at least one alkyl substituent group. 
     
     
         8 . The method of  claim 1  wherein the at least one phenolic antioxidant comprises 
       
         
           
           
               
               
           
         
       
     
     
         9 . The method of  claim 1  wherein the at least one aminic antioxidant comprises an alkylated diphenylamine, phenyl naphthylamine, phenothiazine, imidodibenzyl, or diphenyl phenylene diamine. 
     
     
         10 . The method of  claim 1  wherein the at least one aminic antioxidant comprises an alkylated diarylamine. 
     
     
         11 . The method of  claim 1  wherein the at least one aminic antioxidant comprises 
       
         
           
           
               
               
           
         
       
     
     
         12 . The method of  claim 1  wherein the at least one aminic antioxidant is present in an amount from about 0.5 to about 2 weight percent, and the at least one phenolic antioxidant is present in an amount from about 0.5 to about 4.5 weight percent, based on the total weight of the lubricating oil. 
     
     
         13 . The method of  claim 1  wherein the ratio of the concentration of at least one phenolic antioxidant to the at least one aminic antioxidant is from about 1.5:1 to about 6.0:1 based on the total weight of the lubricant composition. 
     
     
         14 . The method of  claim 1  wherein the lubricating oil base stock comprises a Group I, Group II, Group III, Group IV or Group V base oil. 
     
     
         15 . The method of  claim 1  wherein the at least one Group V base stock is an alkylated naphthalene. 
     
     
         16 . The method of  claim 1  wherein the lubricating oil base stock is present in an amount from about 5 to about 90 weight percent, based on the total weight of the lubricating oil. 
     
     
         17 . The method of  claim 1  wherein the formulated oil further comprises one or more of a viscosity modifier, dispersant, detergent, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, and anti-rust additive. 
     
     
         18 . The method of  claim 1  wherein the lubricating oil is a passenger vehicle engine oil (PVEO) or a commercial vehicle engine oil (CVEO). 
     
     
         19 . A lubricating oil having a composition comprising a lubricating oil base stock as a major component; and at least one aminic antioxidant, at least one phenolic antioxidant, and at least one Group V base stock, as minor components; wherein the lubricating oil base stock is present in an amount from about 1 to about 95 weight percent, based on the total weight of the lubricating oil; wherein the at least one aminic antioxidant is present in an amount from about 0.1 to about 2.5 weight percent, the at least one phenolic antioxidant is present in an amount from about 0.5 to about 5 weight percent, and the at least one Group V base stock is present in an amount from about 1 to about 20 weight percent, all based on the total weight of the lubricating oil; and wherein oxidative stability is improved in a diesel engine lubricated with the lubricating oil, as compared to oxidative stability achieved in a diesel engine lubricated with a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock, as measured by a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048. 
     
     
         20 . The lubricating oil of  claim 19  wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the number of hours to break as measured by Fourier-transform infrared spectroscopy (FT-IR) or by kinematic viscosity at 40° C. (KV40) of said lubricating oil, is greater than about 252 hours as compared to the number of hours to break as measured by FT-IR or KV40 of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock. 
     
     
         21 . The lubricating oil of  claim 19  wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the relative kinematic viscosity at 40° C. (KV40) increase from 300 to 360 hours of said lubricating oil, is less than about 100 percent increase as compared to the relative kinematic viscosity at 40° C. (KV40) increase from 300 to 360 hours of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock. 
     
     
         22 . The lubricating oil of  claim 19  wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the amount of lead present in end of test used oil of said lubricating oil, is less than about 100 ppm as compared to the amount of lead present in end of test used oil of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock. 
     
     
         23 . The lubricating oil of  claim 19  wherein, in a Volvo T-13 Engine Oil Oxidation Test in accordance with ASTM D8048, the FTIR oxidation peak height at end of test, is less than about 175 Abs/cm as compared to the FTIR oxidation peak height at end of test of a lubricating oil containing a minor component other than the at least one aminic antioxidant, the at least one phenolic antioxidant, and the at least one Group V base stock. 
     
     
         24 . The lubricating oil of  claim 19  wherein the at least one phenolic antioxidant comprises a substituted phenol that contains at least one alkyl substituent group; a sterically hindered phenol that contains an alkyl group ortho to the hydroxyl group, or two alkyl groups ortho to the hydroxyl group that occupy the 2-position and 6-position of the phenolic ring, or a mixture thereof; or an alkylene or alkylidene coupled sterically hindered phenol oligomer. 
     
     
         25 . The lubricating oil of  claim 19  wherein the at least one phenolic antioxidant comprises a substituted phenol containing at least one alkyl substituent group. 
     
     
         26 . The lubricating oil of  claim 19  wherein the at least one phenolic antioxidant comprises 
       
         
           
           
               
               
           
         
       
     
     
         27 . The lubricating oil of  claim 19  wherein the at least one aminic antioxidant comprises an alkylated diphenylamine, phenyl naphthylamine, phenothiazine, imidodibenzyl, or diphenyl phenylene diamine. 
     
     
         28 . The lubricating oil of  claim 19  wherein the at least one aminic antioxidant comprises an alkylated diarylamine. 
     
     
         29 . The lubricating oil of  claim 19  wherein the at least one aminic antioxidant comprises 
       
         
           
           
               
               
           
         
       
     
     
         30 . The lubricating oil of  claim 19  wherein the at least one aminic antioxidant is present in an amount from about 0.5 to about 2 weight percent, and the at least one phenolic antioxidant is present in an amount from about 0.5 to about 4.5 weight percent, based on the total weight of the lubricating oil. 
     
     
         31 . The lubricating oil of  claim 19  wherein the ratio of the concentration of at least one phenolic antioxidant to the at least one aminic antioxidant is from about 1.5:1 to about 6.0:1 based on the total weight of the lubricant composition. 
     
     
         32 . The lubricating oil of  claim 19  wherein the lubricating oil base stock comprises a Group I, Group II, Group III, Group IV or Group V base oil. 
     
     
         33 . The lubricating oil of  claim 19  where in the at least one Group V base stock is an alkylated naphthalene. 
     
     
         34 . The lubricating oil of  claim 19  wherein the lubricating oil base stock is present in an amount from about 5 to about 90 weight percent, based on the total weight of the lubricating oil. 
     
     
         35 . The lubricating oil of  claim 19  which further comprises one or more of a viscosity modifier, dispersant, detergent, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, and anti-rust additive. 
     
     
         36 . The lubricating oil of  claim 19  which is a passenger vehicle engine oil (PVEO) or a commercial vehicle engine oil (CVEO).