Marine diesel engine lubricating oil composition having improved high temperature performance

Abstract

A lubricating oil composition containing a base oil of lubricating viscosity, overbased sulfurized alkylphenate detergent or its calcium salt, an overbased alkylsulfonate detergent or its calcium salt, an ashless dispersant, and a zinc dialkyldithiophosphate and/or zinc diaryldithiophosphate is described. The lubricating oil composition provides improved heat stability and anti-wear performance in marine diesel engines operated under severe conditions where the cylinder liner temperature reach 200 to 260° C.

What is claimed is:  
     
         1 . A lubricating oil composition comprising: 
 a) a major amount of a base oil of lubricating viscosity having a kinematic viscosity of 22 to 300 mm 2 /s at 40° C.,    b) 5.0 to 35.0 wt % of an overbased sulfurized alkylphenate detergent,    c) 2.5 to 20.0 wt % of an overbased alkylsulfonate detergent,    d) 0.1 to 3.0 wt % of an ashless dispersant, and    e) 0.1 to 4.0 wt % of a zinc dialkyldithiophosphate or of a zinc diaryldithiophosphate,    wherein the weight ratio between the overbased sulfurized alkylphenate detergent and the overbased alkylsulfonate detergent is in the range of 55:45 to 95:5.    
     
     
         2 . The lubricating oil composition according to    claim 1   , wherein the weight ratio between the overbased sulfurized alkylphenate detergent and the overbased alkylsulfonate detergent is in the range of 60:40 to 90:10.  
     
     
         3 . The lubricating oil composition according to    claim 1   , wherein the overbased sulfurized alkylphenate detergent has a TBN greater than 200.  
     
     
         4 . The lubricating oil composition according to    claim 1   , wherein the overbased alkylsulfonate detergent has a TBN greater than 250.  
     
     
         5 . The lubricating oil composition according to    claim 1   , wherein the ashless dispersant is a succinimide with a polybutenyl group having a molecular weight of 800 to 8,000.  
     
     
         6 . The lubricating oil composition according to    claim 5   , wherein the ashless dispersant is a borated succinimide.  
     
     
         7 . A lubricating oil composition comprising: 
 a) a major amount of a base oil of lubricating viscosity having a kinematic viscosity of 22 to 300 mm 2 /s at 40° C.,    b) 0.4 to 4.0 wt %, based on its calcium content, of an overbased sulfurized calcium alkylphenate detergent,    c) 0.3 to 5.0 wt %, based on its calcium content, of an overbased calcium alkylbenzenesulfonate detergent,    d) 0.001 to 0.1 wt %, based on its nitrogen content, of a nitrogen-containing ashless dispersant, and    e) 0.0075 to 0.3 wt %, based on its phosphorus content, of a zinc dialkyldithiophosphate or of a zinc diaryldithiophosphate,    wherein the weight ratio between the overbased sulfurized calcium alkylphenate detergent and the overbased calcium alkylbenzenesulfonate detergent is in the range of 55:45 to 95:5.    
     
     
         8 . The lubricating oil composition according to    claim 7   , wherein the weight ratio between the overbased sulfurized alkylphenate detergent and the overbased alkylsulfonate detergent is in the range of 60:40 to 90:10.  
     
     
         9 . The lubricating oil composition according to    claim 7   , wherein the overbased sulfurized calcium alkylphenate detergent has a TBN greater than 110.  
     
     
         10 . The lubricating oil composition according to    claim 7   , wherein the overbased calcium alkylbenzenesulfonate detergent has a TBN greater than 120.  
     
     
         11 . The lubricating oil composition according to    claim 7   , wherein the nitrogen-containing ashless dispersant is a succinimide with a polybutenyl group having a molecular weight of 800 to 8,000.  
     
     
         12 . The lubricating oil composition according to    claim 11   , wherein the ashless dispersant is a borated succinimide.  
     
     
         13 . A lubricating oil additive concentrate comprising: 
 a) 1.0 to 50.0 wt % of a compatible organic diluent,    b) 5.0 to 90.0 wt % of an overbased sulfurized alkylphenate detergent,    c) 5.0 to 90.0 wt % of an overbased alkylsulfonate detergent,    d) 0.5 to 50.0 wt % of an ashless dispersant,    e) 0.5 to 20 wt % of a zinc dialkyldithiophosphate or of a zinc diaryldithiophosphate,    wherein the weight ratio between the overbased sulfurized alkylphenate detergent and the overbased alkylsulfonate detergent is in the range of 55:45 to 95:5.    
     
     
         14 . The lubricating oil additive concentrate according to    claim 13   , wherein the weight ratio between the overbased sulfurized alkylphenate detergent and the overbased alkylsulfonate detergent is in the range of 60:40 to 90:10.  
     
     
         15 . The lubricating oil additive concentrate according to    claim 13   , wherein the overbased sulfurized alkylphenate detergent has a TBN greater than 200.  
     
     
         16 . The lubricating oil additive concentrate according to    claim 13   , wherein the overbased alkylsulfonate has a TBN greater than 200.  
     
     
         17 . The lubricating oil additive concentrate according to    claim 13   , wherein the ashless dispersant is a succinimide with a polybutenyl group having a molecular weight of 800 to 8,000.  
     
     
         18 . The lubricating oil additive concentrate according to    claim 17   , wherein the ashless dispersant is a borated succinimide.  
     
     
         19 . A lubricating oil additive concentrate comprising: 
 a) 1.0 to 50.0 wt % of a compatible organic diluent,    b) 0.4 to 9.0 wt %, based on its calcium content, of an overbased sulfurized alkylphenate detergent,    c) 0.6 to 16.0 wt %, based on its calcium content, of an overbased alkylbenzenesulfonate detergent,    d) 0.005 to 1.0 wt %, based on its nitrogen content, of a nitrogen-containing ashless dispersant,    e) 0.005 to 1.5 wt %, based on its phosphorus content, of a zinc dialkyldithiophosphate or of a zinc diaryldithiophosphate,    wherein the weight ratio between the overbased sulfurized alkylphenate detergent and the overbased alkylsulfonate detergent is in the range of 55:45 to 95:5.    
     
     
         20 . The lubricating oil additive concentrate according to    claim 19   , wherein the weight ratio between the overbased sulfurized alkylphenate detergent and the overbased alkylsulfonate detergent is in the range of 60:40 to 90:10.  
     
     
         21 . The lubricating oil additive concentrate according to    claim 19   , wherein the overbased sulfurized calcium alkylphenate detergent has a TBN greater than 200.  
     
     
         22 . The lubricating oil additive concentrate according to    claim 19   , wherein the overbased calcium alkylbenzenesulfonate detergent has a TBN greater than 200.  
     
     
         23 . The lubricating oil additive concentrate according to    claim 19   , wherein the nitrogen-containing ashless dispersant is a succinimide with a polybutenyl group having a molecular weight of 800 to 8,000.  
     
     
         24 . The lubricating oil additive concentrate according to    claim 23   , wherein the ashless dispersant is a borated succinimide.  
     
     
         25 . A method of improving the heat stability and anti-wear performance at high temperatures of an internal combustion engine, said method comprising lubricating the internal combustion engine with a lubricating oil composition according to    claim 1   .  
     
     
         26 . A method of improving the heat stability and anti-wear performance at high temperatures of an internal combustion engine according to    claim 25   , wherein the internal combustion engine is a two-stroke cross-head diesel engine.  
     
     
         27 . A method for producing a lubricating oil composition comprising blending the components according to    claim 1   .  
     
     
         28 . A lubricating oil composition produced by the method according to    claim 27   .