Reducing High-Aqueous Content Sludge in Diesel Engines

Abstract

Formation of high-aqueous content sludge may be reduced in a sump lubricated diesel engine lubricated with a lubricating oil formulation that contains at least 0.07 or 0.08 weight percent nitrogen derived from one or more nitrogen-containing ashless dispersants, by including in the lubricant a polyalkylene oxide.

1 . A method for reducing accumulation of high-aqueous content sludge in a sump-lubricated diesel engine lubricated with a lubricating oil formulation that contains at least one nitrogen-containing dispersant and optionally at least one dispersant viscosity modifier or polymeric material, wherein {the weight percent nitrogen derived from one or more nitrogen-containing ashless dispersants and nitrogen-containing dispersant viscosity modifiers} plus {0.1 times the weight percent of any aromatic carbon provided by the following aromatic containing materials: polymeric materials, dispersants, and dispersant viscosity modifiers} is at least 0.07, said method comprising:
 including in said lubricant at least about 0.05 percent by weight of a polyalkylene oxide.   
     
     
         2 . The method of  claim 1  wherein the aromatic containing materials upon which the percent aromatic carbon is calculated are polymeric materials, dispersant viscosity modifiers, and dispersants other than Mannich dispersants. 
     
     
         3 .- 4 . (canceled) 
     
     
         5 . The method of  claim 1  wherein the total of {weight percent nitrogen derived from one or more nitrogen-containing ashless dispersants} plus {0.1 times the weight percent aromatic carbon provided by the recited aromatic materials} is at least 0.08 weight percent. 
     
     
         6 . (canceled) 
     
     
         7 . The method of  claim 1  wherein the nitrogen derived from one or more nitrogen-containing ashless dispersants is at least 0.07 weight percent. 
     
     
         8 . The method of  claim 1  wherein the amount of the nitrogen derived from one or more nitrogen-containing ashless dispersants is at least 0.08 weight percent 
     
     
         9 . The method of  claim 1  wherein the diesel engine has restricted crankcase ventilation. 
     
     
         10 . The method of  claim 1  wherein the engine contains a rocker cover which is susceptible to formation of high-aqueous content sludge thereon. 
     
     
         11 . The method of  claim 1  wherein the lubricating oil formulation contains at least about 3.0 percent by weight of one or more nitrogen-containing ashless dispersants. 
     
     
         12 . The method of  claim 1  wherein the nitrogen-containing ashless dispersant comprises a succinimide dispersant. 
     
     
         13 . The method of  claim 1  wherein the lubricant formulation comprises a dispersant viscosity modifier. 
     
     
         14 . The method of  claim 1  wherein the amount of the polyalkylene oxide is about 0.1 to about 3 percent by weight. 
     
     
         15 . (canceled) 
     
     
         16 . The method of  claim 1  wherein the polyalkylene oxide is a polyethylene oxide, a polypropylene oxide, a polytetramethylene oxide, or a mixed poly(ethylene-propylene) oxide, having a number average molecular weight of about 500 to about 10,000. 
     
     
         17 . The method of  claim 1  wherein the polyalkylene oxide is a diol. 
     
     
         18 . The method of  claim 1  wherein the lubricant comprises an oil of lubricating viscosity and further comprises at least one additional component selected from the group consisting of an overbased metal detergent, a zinc dialkyldithiophosphate, and an antioxidant. 
     
     
         19 . (canceled) 
     
     
         20 . A lubricant composition suitable for reducing accumulation of high-aqueous content sludge in a sump-lubricated diesel engine, comprising:
 an oil of lubricating viscosity;   one or more nitrogen-containing ashless dispersants or dispersant viscosity modifiers such that the formulation contains at least one nitrogen-containing dispersant and optionally at least one dispersant viscosity modifier or polymeric material, wherein {the weight percent nitrogen derived from one or more nitrogen-containing ashless dispersants and nitrogen-containing dispersant viscosity modifiers} plus {0.1 times the weight percent of any aromatic carbon provided by the following aromatic containing materials: polymeric materials, dispersants, and dispersant viscosity modifiers} is at least 0.07;   wherein the lubricant composition comprises a nitrogen-containing dispersant viscosity modifier;   
       and
 at least about 0.05 percent by weight of a polyalkylene oxide. 
 
     
     
         21 . The lubricant composition of  claim 20  wherein the nitrogen derived from one or more nitrogen-containing ashless dispersants is at least 0.07 weight percent. 
     
     
         22 . The lubricant composition of  claim 20 , further comprising at least one additional additive selected from the group consisting of detergents, metal salts of phosphorus acids, viscosity modifiers, antioxidants, corrosion inhibitors, antiwear agents, pour point depressants, and anti-foam agents. 
     
     
         23 . (canceled) 
     
     
         24 . The lubricant composition of  claim 20  wherein the oil of lubricating viscosity comprises an API Group II or Group III or Group IV oil or a mixture thereof. 
     
     
         25 . A method for reducing accumulation of high-aqueous content sludge in a sump-lubricated diesel engine lubricated with a lubricating oil formulation that contains at least 0.08 weight percent nitrogen derived from one or more nitrogen-containing ashless dispersants, said method comprising:
 including in said lubricant at least about 0.05 percent by weight of a polyalkylene oxide.