Method of lubricating an internal combustion engine

Abstract

The invention provides a method of lubricating an internal combustion engine equipped with a centrifugal oil mist separator, wherein the lubricant contains 0.1 wt % to 8 wt % soot resulting from operation of the engine, and wherein the lubricant composition comprises an oil of lubricating viscosity, and 0.2 wt % to 3 wt % of a soot dispersing additive, wherein the soot dispersing additive comprises a polymer chain having a number average molecular weight of 500 to 20,000, and wherein the soot dispersing additive has a shear stability index of 0 to 20.

1 - 35 . (canceled) 
     
     
         36 . A method of lubricating an internal combustion engine equipped with a centrifugal oil mist separator, wherein the lubricant contains 0.1 wt % to 8 wt % soot resulting from operation of the engine, and wherein the lubricant composition comprises an oil of lubricating viscosity, and 0.2 wt % to 3 wt % of a soot dispersing additive, wherein the soot dispersing additive comprises a polymer chain having a number average molecular weight of 500 to 20,000 and a shear stability index of 0 to 20. 
     
     
         37 . The method of  claim 36 , wherein the lubricating composition has (i) a sulfur content of 0.5 wt % or less, (ii) a phosphorus content of 0.15 wt % or less, and (iii) a sulfated ash content of 0.5 wt % to 1.5 wt %. 
     
     
         38 . The method of  claim 36 , wherein the lubricating composition has at least one of (i) a sulfur content of 0.2 wt % to 0.4 wt %, (ii) a phosphorus content of 0.08 wt % to 0.15 wt %, and (iii) a sulfated ash content of 0.5 wt % to 1.5 wt %. 
     
     
         39 . The method of  claim 38 , wherein the lubricating composition has a sulfated ash content of 0.5 wt % to 1.2 wt %. 
     
     
         40 . The method of  claim 36 , wherein the lubricating composition has a total base number (TBN) content of at least 5 mg KOH/g. 
     
     
         41 . The method of  claim 40 , wherein the lubricating composition has a total base number (TBN) content of 6 to 13 mg KOH/g. 
     
     
         42 . The method of  claim 36 , wherein the vehicle powered by a compression-ignition internal combustion engine has a maximum laden mass over 3,500 kg. 
     
     
         43 . The method of  claim 36 , wherein the soot dispersing additive has a shear stability index of 0 to 10. 
     
     
         44 . The method of  claim 36 , wherein the soot dispersing additive is selected from the group consisting of a dispersant viscosity modifier comprising an aromatic amine moiety, a dispersant comprising an aromatic amine moiety and mixtures thereof. 
     
     
         45 . The method of  claim 44 , wherein the soot dispersing additive comprises a dispersant viscosity modifier comprising an aromatic amine moiety wherein the dispersant viscosity modifier is an olefin copolymer functionalised with an aromatic moiety. 
     
     
         46 . The method of  claim 45 , wherein the olefin copolymer has a shear stability index of 0 to 10. 
     
     
         47 . The method of  claim 45 , wherein the dispersant viscosity modifier is derived from reacting the olefin copolymer with an acylating agent and an aromatic amine having a primary or secondary amino group. 
     
     
         48 . The method of  claim 47 , wherein the aromatic amine is selected from the group consisting of 4-aminodiphenylamine, aldehyde coupled 4-aminodiphenylamine, nitro-aniline, 4-nitrophenylazoaniline, and mixtures thereof. 
     
     
         49 . The method of  claim 36 , wherein the soot dispersing additive is a dispersant comprising an aromatic amine moiety obtained by reacting a carboxylic functionalised polymer with an amine having at least 4 aromatic groups and an aldehyde. 
     
     
         50 . The method of  claim 36 , wherein the lubricating composition further comprises a phenolic or an aminic antioxidant or mixtures thereof, and wherein the antioxidant is present at 0.1 wt % to 3 wt %. 
     
     
         51 . The method of  claim 36 , wherein the lubricating composition further comprises an overbased sulfonate detergent present at 0.01 wt % to 0.9 wt %. 
     
     
         52 . The method of  claim 51 , wherein the overbased sulfonate detergent has a metal ratio of 12 to less than 20. 
     
     
         53 . The method of  claim 51 , wherein the overbased sulfonate detergent has a metal ratio of 20 to 30. 
     
     
         54 . The method of  claim 51 , wherein the lubricating composition further comprises 0.01 wt % to 2 wt % of a detergent different from the overbased sulfonate detergent, wherein the further detergent is selected from the group consisting of borated and non-borated non-sulfur containing phenates, borated and non-borated sulfur containing phenates, borated and non-borated sulfonates, borated and non-borated salixarates, borated and non-borated salicylates, and mixtures thereof. 
     
     
         55 . The method of  claim 36 , wherein the lubricating composition further comprises a “hybrid” detergent formed with mixed surfactant systems comprising a phenate or sulfonate component. 
     
     
         56 . The method of  claim 36 , wherein the lubricating composition further comprises a phosphorus-containing antiwear agent. 
     
     
         57 . The method of  claim 36 , wherein the lubricating composition further comprises an ashless succinimide dispersant different from the soot-dispersing additive, wherein the succinimide dispersant is present at 1 wt % to 8 wt %. 
     
     
         58 . The method of  claim 57 , wherein the succinimide dispersant comprises a polyisobutylene succinimide, wherein the polyisobutylene from which polyisobutylene succinimide is derived has a number average molecular weight of 350 to 5000. 
     
     
         59 . The method of  claim 57 , wherein the succinimide dispersant comprises a polyisobutylene succinimide, wherein the dispersant has a TBN of at least 40 mg KOH/g and is present in an amount 1.2 wt % to 5 wt % of the lubricating composition. 
     
     
         60 . The method of  claim 36 , wherein the internal combustion engine has a steel surface on a cylinder bore, cylinder block, or piston ring. 
     
     
         61 . The method of  claim 36 , wherein the internal combustion engine has a surface of steel, or an aluminum alloy, or an aluminum composite. 
     
     
         62 . The method of  claim 36 , wherein the oil mist separator is a centrifugal oil mist separator, wherein the centrifugal oil mist separator rotates at 2500 to 10000 rpm. 
     
     
         63 . The method of  claim 36 , wherein the internal combustion engine has a closed crankcase ventilation.