Lubricating oil compositions

Abstract

Lubricating oil compositions for residual fuel oil-fuelled diesel engines for marine and stationary applications comprising, or made by admixing: (a) a basestock of lubricating viscosity, in a major amount; and (b) an oil-soluble or oil-dispersible molybdenum compound, in a minor amount; wherein the oil composition has a TBN from 20 to 100 as measured according to ASTM D-2896 and a viscosity at 100° C. in the range from 9 to 30 mm 2 s −1 as measured according to ASTM D-445. The lubricating oil compositions of the present invention demonstrate improved cylinder liner wear performance.

What is claimed is:  
     
         1 . A lubricating oil composition for a residual fuel oil-fuelled diesel engine for marine and stationary applications, comprising: 
 (a) an oil of lubricating viscosity, in a major amount; and    (b) an oil soluble or oil-dispersible molybdenum compound, in a minor amount;    wherein the oil composition has a TBN from 20 to 100 as measured according to ASTM D-2896 and a viscosity at 100° C. in the range from 9 to 30 mm 2 s −1  as measured according to ASTM D-445.    
     
     
         2 . The lubricating oil composition as claimed in  claim 1 , wherein the molybdenum compound is polynuclear.  
     
     
         3 . The lubricating oil composition as claimed in  claim 2 , wherein the molybdenum compound is trinuclear.  
     
     
         4 . The lubricating oil composition as claimed in  claim 1 , in the form of a residual-fuelled cross-head marine diesel engine lubricating oil composition having a TBN from 30 to 95 and a viscosity at 100° C. in the range from 9 to 25 mm 2 s −1 .  
     
     
         5 . The lubricating oil composition as claimed in  claim 1 , further comprising: 
 (c) a detergent composition, which comprises one or more overbased metal detergents.    
     
     
         6 . The lubricating oil composition as claimed in  claim 1 , further comprising: 
 (d) a dispersant, which has a hydrocarbon backbone of molecular weight from 100 to 10000.    
     
     
         7 . The lubricating oil composition as claimed in  claim 1 , wherein the molybdenum compound is present in an amount from 1 to 10000 ppm of molybdenum by mass, based on the mass of the oil composition.  
     
     
         8 . The lubricating oil composition as claimed in  claim 1 , further comprising a residual fuel oil.  
     
     
         9 . A combination of a cylinder of a two-stroke cross-head marine diesel engine and a lubricating oil composition as claimed in  claim 1 , wherein the cylinder is characterised by a power output of 4000 kW or greater.  
     
     
         10 . A method of reducing corrosive wear in a cylinder liner of a residual fuel oil-fuelled diesel engine comprising supplying to the walls of the cylinder a lubricating oil composition as claimed in  claim 1 .  
     
     
         11 . An additive composition comprising: 
 (a) an oil-soluble or oil-dispersible molybdenum compound; and    (b) one or more co-additives;    wherein the additive composition contains (a) and (b) in an amount to provide a lubricating oil composition having a TBN from 20 to 100 as measured according to ASTM D-2896 and a viscosity at 100° C. in the range from 9 to 30 mm 2 s −1  as measured according to ASTM D-445, when the lubricating oil composition contains 5 to 40 mass % of the additive composition.