Marine diesel engine lubricating oil composition

Abstract

A marine diesel lubricating oil composition having a TBN from about 5 to about 120 containing a base oil of lubricating viscosity, an overbased alkylaryl C 10-40 sulfonate detergent and an overbased isomerized C 10-40 normal alpha olefin based phenate detergent, wherein the weight ratio of the overbased sulfonate detergent to the overbased isomerized normal alpha olefin based phenate detergent ranges from 1:9 to 9:1.

What is claimed is: 
     
         1 . A marine diesel lubricant composition having a TBN from about 5 to about 120 comprising:
 (a) a major amount of a base oil of lubricating viscosity;   (b) a first detergent that is an alkaline earth metal salt of an overbased C 10-40  alkylarylsulfonate detergent; and   (c) a second detergent that is an alkaline earth metal salt of an overbased isomerized C 10-40  normal alpha olefin based sulfurized phenate detergent;   
       wherein the weight ratio of the first detergent to the second detergent ranges from 1:9 to 9:1. 
     
     
         2 . The composition of  claim 1 , wherein the overbased alkylsulfonate detergent and the overbased isomerized normal alpha olefin based phenate detergent are both an overbased calcium salt. 
     
     
         3 . The composition of  claim 1 , wherein the alkyl substituent of the overbased isomerized normal alpha olefin based phenate detergent is made by isomerizing a C 14 -C 24  normal alpha olefin. 
     
     
         4 . The composition of  claim 1 , wherein the base oil of lubricating viscosity is a Group I base oil. 
     
     
         5 . The composition of  claim 1 , wherein the base oil of lubricating viscosity is a Group II base oil. 
     
     
         6 . The composition of  claim 1 , wherein the composition does not contain a glycerol ester or a borated glycerol ester. 
     
     
         7 . The composition of  claim 1 , wherein overbased isomerized normal alpha olefin based phenate detergent is an alkylated hydroxyl compound wherein the alkyl substituent of the hydroxyl compound is a residue of at least one olefin having from about 15 to about 99 wt. % branching. 
     
     
         8 . The composition of  claim 1 , wherein the overbased isomerized normal alpha olefin based phenate detergent is an alkylated hydroxyl compound wherein the alkyl substituent of the hydroxyl compound is a residue of at least one olefin having from about 15 to about 99 wt. % branching. 
     
     
         9 . A method of operating a marine diesel engine comprising lubricating the engine with a lubricating oil composition having a TBN of from about 5 to about 120 comprising:
 (a) a major amount of a base oil of lubricating viscosity;   (b) a first detergent that is an alkaline earth metal salt of overbased C 10-40  alkylarylsulfonate detergent; and   (c) a second detergent that is an alkaline earth metal salt of overbased isomerized C 10-40  normal alpha olefin based sulfurized phenate detergent;   
       wherein the weight ratio of the first detergent to the second detergent ranges from 1:9 to 9:1. 
     
     
         10 . A method of lubricating the cylinder of a marine diesel engine comprising lubricating the cylinder with a lubricating oil composition having a TBN of about 5 to about 120 comprising:
 (a) a major amount of a base oil of lubricating viscosity;   (b) a first detergent that is an alkaline earth metal salt of an overbased C 10-40  alkylarylsulfonate detergent; and   (c) a second detergent that is an alkaline earth metal salt of an overbased isomerized C 10-40  normal alpha olefin based sulfurized phenate detergent;   wherein the weight ratio of the first detergent to the second detergent ranges from 1:9 to 9:1.