Lubricant compositions

Abstract

A marine diesel engine lubricant composition having a TBN of at least 10 and preferably a VI of at least 90, comprises a major amount of oil of lubricating viscosity, and admixed therewith, minor amounts of an ashless antiwear additive and a metal detergent in the form of (i) an overbased metal detergent having a TBN at least 300, preferably at least 330, more preferably at least 400, and comprising a surfactant system derived from at least two surfactants, and/or (ii) a metal detergent other than (i); provided that, if detergent (ii) is present, the composition does not contain a minor amount of an extreme pressure additive, being up to 5.0 mass % based on the total mass of the composition.

1 . A marine diesel engine lubricant composition having a TBN of at least 10, such as at least 20, and preferably a viscosity index of at least 90, preferably at least 100, more preferably at least 110, the composition comprising, or being provided by admixing, a major amount of oil of lubricating viscosity and a minor amount of 
 (A) an ashless antiwear additive; and    (B) a metal detergent in the form of 
 (i) an overbased metal detergent having a TBN at least 300, preferably at least 330, more preferably at least 400, and comprising a surfactant system derived from at least two surfactants, and/or  
 (ii) a metal detergent other than (i);  
 provided that, if detergent (ii) is present, the composition does not contain a minor amount of an extreme pressure additive, being up to 5.0 mass % based on the total mass of the composition.  
   
     
     
         2 . A method of making a marine diesel engine lubricant composition having a TBN of at least 10, such as at least 20, and preferably a viscosity index of at least 90, preferably at least 100, more preferably at least 110, comprising blending a major amount of oil of lubricating viscosity and minor amounts of (A) and (B) as defined in    claim 1   , provided that, if detergent (ii) is blended, a minor amount of an extreme pressure agent, being up to 5.0 mass % based on the total mass of the composition, is not blended.  
     
     
         3 . The composition or method as claimed in    claim 1    or    claim 2    wherein an extreme pressure agent is absent.  
     
     
         4 . The composition or method as claimed in any of the preceding claims wherein the TBN of the composition is at least 40, preferably in the range of from 60 to 100.  
     
     
         5 . The composition or method as claimed in any of the preceding claims wherein the viscosity index is preferably at least 115, more preferably at least 120.  
     
     
         6 . The composition or method as claimed in any of the preceding claims wherein the amount of ashless antiwear additive is at least 0.01, preferably at least 0.1, such as in the range of from 0.1 to 10, mass %, based on the mass of the composition.  
     
     
         7 . The composition or method as claimed in any of the preceding claims wherein the antiwear additive is a sulfur-, phosphorus-, or boron-containing additive, or a mixture thereof.  
     
     
         8 . The composition or method as claimed in    claim 7    wherein the antiwear additive comprises a sulfur-containing boroester compound, being a borate ester having the general formula (I):  
                 
 
       wherein R 1  represents a hydrocarbyl group having from 4 to 12 carbon atoms, R 2  and R 3  independently represent —(OR 4 ) n SR 1  or —(OR 4 ) n SR 1 OH; R 4  represents a hydrocarbyl group having from 1 to 6 carbon atoms; n is an integer of from 1 to 4; and l and m are independently 0, 1 or 2; 
 a cyclic metaborate ester having the general formula (II):  
                 
 
 wherein n, R 1  and R 4 , are defined as in formula (I); or  
 a mixture of a borate ester of formula (I) and a metaborate ester of formula (II).  
 
     
     
         9 . The composition or method as claimed in any of the preceding claims wherein detergent (B) (ii) is an overbased metal detergent.  
     
     
         10 . The composition or method as claimed in    claim 9    wherein the overbased metal detergent has a TBN of at least 200, preferably at least 250, especially at least 300, such as up to 600.  
     
     
         11 . The composition or method as claimed in any of the preceding claims wherein the metal in (B) is calcium.  
     
     
         12 . The composition or method as claimed in any of the preceding claims wherein (B) (ii) comprises at least two overbased metal detergents and the mass to mass proportion of any one such detergent to any other such detergent is in the range of from 5:95 to 95:5.  
     
     
         13 . The composition or method as claimed in    claim 12    wherein the mass to mass proportion is in the range of from 20:80 to 80:20, preferably from 70:30 to 30:70, such as from 60:40 to 40:60.  
     
     
         14 . The composition or method as claimed in any of the preceding claims wherein the metal detergent is a phenate or a sulfonate.  
     
     
         15 . A marine diesel engine lubricant composition comprising, or being provided by admixing, a major amount of oil of lubricating viscosity and a minor amount of (A) a sulfur-containing boroester compound as defined in    claim 8   , and (B) a metal detergent.  
     
     
         16 . A method of making a marine diesel engine lubricant composition comprising blending a major amount of oil of lubricating viscosity and a minor amount of an additive as defined in    claim 15   .  
     
     
         17 . A method of reducing the piston ring and cylinder liner wear of a marine diesel engine comprising lubricating the engine with a lubricant composition as claimed, or made by a method as claimed, in any of the preceding claims.  
     
     
         18 . The use of a lubricant composition to reduce the piston ring and cylinder liner wear of a marine diesel engine which comprises lubricating the engine with a composition as claimed, or made by a method as claimed, in any of the preceding claims.  
     
     
         19 . A method of lubricating a marine diesel engine which comprises supplying to the engine a marine diesel engine lubricant composition as claimed, or made by a method as claimed, in any of    claims 1    to    16   .  
     
     
         20 . A method as claimed in    claim 19    wherein the engine is supplied with a fuel having a sulfur-content, expressed as elemental sulfur, of not greater than 1.5, such as 0.5 to 1, mass %.  
     
     
         21 . The composition, method or use as claimed in any of the preceding claims wherein the marine diesel engine is a cross-head diesel engine.  
     
     
         22 . The composition, method or use as claimed in any of    claims 1    to    20    wherein the composition is a marine diesel cylinder lubricant.