Selected comb polymers include specified amounts of macromonomer and imide functionalization. Further, a method is useful for the preparation of such comb polymers. Lubricant compositions including such comb polymers are useful for reducing wear and fuel consumption of lubricant compositions, especially of engine oil (EO) compositions.

A method for minimizing power loss, reducing a fuel consumption and/or for reducing and/or avoiding deposits in a fuel system in the direct injection diesel engines. The method contains adding a copolymer to a fuel composition, wherein the copolymer contains, in a copolymerized form: (A) an ethylenically unsaturated mono- or dicarboxylic acid or a derivative thereof, (B) an -olefin having from 12 to 30 carbon atoms, (C) optionally an additional aliphatic or cycloaliphatic olefin which has at least 4 carbon atoms and is different from monomer (B) and (D) optionally an additional copolymerizable monomers other than monomers (A), (B) and (C), anhydride or carboxylic acid functionalities present in the copolymer are partly reacted with at least one compound (E) comprising an alcohol group and/or an amino group, and the anhydride functionalities present in the copolymer are hydrolysed and/or carboxylic ester functionalities present in the copolymer are partly hydrolyzed.

Selected comb polymers contain specified amounts of macromonomer and nitrogen-containing (meth)acrylates. Lubricant compositions can contain such comb polymers. The selected comb polymers can be used as solubilizers in lubricant compositions, especially in engine oil (EO) compositions.

Selected comb polymers contain specified amounts of macromonomer and nitrogen-containing (meth)acrylates. Lubricant compositions can contain such comb polymers. The selected comb polymers can be used as solubilizers in lubricant compositions, especially in engine oil (EO) compositions.

A water-based lubricant for plastic working of a metallic material is obtained by adding to a water-based medium: (A) a polymer and/or a salt thereof containing a carboxylic acid or a derivative thereof as a constituent monomer; (B) an oxoacid of tungsten, of silicon, or of phosphorus, or a condensate thereof, and/or a salt thereof; (C) a hydroxide of an alkali metal; and (D) a lubricating component (D), and the solid content weight ratio (A)/[(A)+(B)+(C)+(D)] is 0.05 to 0.4.

A water-based lubricant for plastic working of a metallic material is obtained by adding to a water-based medium: (A) a polymer and/or a salt thereof containing a carboxylic acid or a derivative thereof as a constituent monomer; (B) an oxoacid of tungsten, of silicon, or of phosphorus, or a condensate thereof, and/or a salt thereof; (C) a hydroxide of an alkali metal; and (D) a lubricating component (D), and the solid content weight ratio (A)/[(A)+(B)+(C)+(D)] is 0.05 to 0.4.

A viscosity index improver comprising a reaction product of (i) an acylated copolymer obtainable by acylating a copolymer of ethylene and one or more C.sub.3-C.sub.10 alpha-olefins having an Mn of 3,000 to 250,000 g/mol; and (ii) a compound of the formulae (I)-(V):

##STR00001##

wherein R.sub.1, R.sub.6, R.sub.8, R.sub.9, R.sub.10, R.sub.12 and R.sub.15 are independently selected from a hydrogen and an optionally substituted linear or branched alkyl or alkenyl group, and R.sub.2, R.sub.3, R.sub.4, and R.sub.5 R.sub.7, R.sub.11, R.sub.13, R.sub.14, R.sub.16, and R.sub.17 are independent selected from an optionally substituted linear or branched alkyl or alkenyl group, and a sum of the number of carbon atoms in each compound of the formulae (I)-(V) is from 6 to 31.

A viscosity index improver comprising a polymer which has a high viscosity index and good shear stability and which exhibits sufficient solubility in a lubricating base oil, a process for producing the same, and a lubricating oil composition containing the viscosity index improver are provided, wherein the viscosity index improver comprising a polymer satisfying the following (1) to (4): (1) weight-average molecular weight (Mw) of 200,000 or more and 600,000 or less; (2) number-average molecular weight (Mn) of 90,000 or more; (3) molecular weight distribution (Mw/Mn) of 4.0 or less; and (4) branching degree of 1.0 or more.

A viscosity index improver comprising a polymer which has a high viscosity index and good shear stability and which exhibits sufficient solubility in a lubricating base oil, a process for producing the same, and a lubricating oil composition containing the viscosity index improver are provided, wherein the viscosity index improver comprising a polymer satisfying the following (1) to (4): (1) weight-average molecular weight (Mw) of 200,000 or more and 600,000 or less; (2) number-average molecular weight (Mn) of 90,000 or more; (3) molecular weight distribution (Mw/Mn) of 4.0 or less; and (4) branching degree of 1.0 or more.

The present invention is directed to a use of a lubricant in a diesel engine to disperse soot produced by the diesel engine, the soot being dispersed without adversely affecting the viscosity of the lubricant; the lubricant comprising a major amount of oil of lubricating viscosity and a minor amount of a dispersant comprising (i) one or more olefin, (ii) one or more carboxylic acid, (iii) one or more polyetheramines and (iv) one or more aromatic amines along with co-additives.