Long life engine oil composition with low or no zinc content

Abstract

A lubricating oil especially useful as a natural gas engine lubricating oil that has extended life as evidenced by reductions in viscosity increase, oxidation and nitration relative to current commercial and reference oils is provided. The oil comprises a major amount of a base oil of lubricating viscosity and a mixture of metallic detergents comprising: (i) a neutral calcium alkylsalicylate detergent and (ii) a second neutral or overbased metallic detergent or mixture of detergents other than neutral calcium alkylsalicylate selected from the group consisting of calcium and barium sulfonates, phenates and alkylsalicylates. The composition is further characterized as having low or no zinc.

1 . A lubricating composition having long life as evidenced by a reduction in viscosity increase, oxidation and nitration, comprising:
 (a) a major amount of an oil of lubricating viscosity;   (b) a mixture of metallic detergents comprising:
 (i) a first neutral calcium alkylsalicylate detergent, and 
 (ii) a second neutral or overbased metallic detergent or mixture of metallic detergents selected from the group consisting of calcium and barium sulfonates, phenates, and alkylsalicylates, and excluding neutral calcium alkylsalicylates, and 
   (c) from 0.0 mass % to about 0.1 mass % of a zinc dialkyldithiophosphate based on the total mass of the composition.   
     
     
         2 . The composition of  claim 1  wherein the first metallic detergent, (i), is present in the range of about 0.1 mass % to about 2.1 mass %, based on the total mass of the composition. 
     
     
         3 . The composition of  claim 1 , wherein the second metallic detergent or mixture of detergents (ii) is present in the range of about 0.8 mass % to about 10 mass %, based on the total mass of the composition. 
     
     
         4 . The composition of  claim 1  wherein the combined amount of metallic detergents (i) and (ii) is sufficient to provide the total composition with a sulfated ash range of from about 0.3 mass % to about 2.2 mass %. 
     
     
         5 . The composition of  claim 4  including 0.0 mass % zinc dialkyldithiophosphate. 
     
     
         6 . The composition of  claim 5  wherein the second metallic detergent (ii) is a mixture of neutral barium sulfonate and neutral calcium sulfonate. 
     
     
         7 . The composition of  claim 5  wherein the second metallic detergent (ii) is a mixture of overbased calcium sulfonate and neutral calcium sulfonate. 
     
     
         8 . The composition of  claim 5  wherein the second metallic detergent (ii) is a neutral calcium sulfonate. 
     
     
         9 . A lubricating oil composition having long life as evidenced by a reduction in viscosity increase, oxidation and nitration, comprising:
 (a) a major amount of an oil of lubricating viscosity;   (b) a mixture of metallic detergents comprising:
 (i) a neutral calcium alkylsalicylate detergent in an amount ranging from about 0.1 mass % to about 2.1 mass %, based on the total mass of the composition, and 
 (ii) a second neutral or overbased metallic detergent or mixture of detergents other than neutral calcium alkylsalicylate selected from the group consisting of calcium and barium sulfonates, phenates, and alkylsalicylates wherein the amount of metallic detergent is sufficient to provide the total composition with a sulfated ash range of from about 0.3 mass % to about 2.2 mass %, and 
   (c) from 0.0 mass % to about 0.1 mass % of a zinc dialkyldithiophosphate based on the total mass of the composition.   
     
     
         10 . The composition of  claim 9  wherein the mass ratio of (i) to (ii) is in the range of about 0.1:1.0 to about 3:1.9. 
     
     
         11 . A method for extending the life of a lubricating oil as evidenced by a reduction in viscosity increase, oxidation and nitration, the method comprising:
 adding to the lubricating oil:   (a) a mixture of metallic detergents, comprising
 (i) a neutral calcium salicylate detergent and 
 (ii) a second neutral or overbased metallic detergent or mixture of detergents other than neutral calcium alkylsalicylate selected from the group consisting of calcium and barium sulfonates, phenates, and alkylsalicylates, wherein the amount of metallic detergent is sufficient to provide the total composition with a sulfated ash range of from about 0.3 mass % to about 2.2 mass %, and 
   (b) from 0.0 mass % to about 0.1 mass % of a zinc dialkyldithiophosphate based on the total mass of the composition   
     
     
         12 . The method of  claim 11  wherein the amount of the neutral calcium salicylate detergent added is in the range of 0.1 to 2.1 mass % based on the total mass of the composition. 
     
     
         13 . In a lubricating composition, the use of a mixture of metallic detergents comprising:
 (i) a first neutral calcium alkylsalicylate detergent, and   (ii) a second neutral or overbased metallic detergent or mixture of metallic detergents selected from the group consisting of calcium and barium sulfonates, phenates, and alkylsalicylates, excluding neutral calcium alkylsalicylates.   
     
     
         14 . The use of  claim 13 , wherein the amount of metallic detergents is sufficient to provide a composition with a sulfated ash range of from about 0.3 mass % to about 2.2. mass %. 
     
     
         15 . The use of  claim 13 , wherein the amount of first metallic detergent (i) is in the range of from about 0.1 mass % to about 2.1 mass %, based on the total mass of the composition. 
     
     
         16 . The use of any of  claims 13  to  15 , wherein the amount of second metallic detergent or mixture of metallic detergents is in the range of from about 0.8 mass % to about 10 mass %.