A lubricating oil composition may include a base oil (A), succinimide (B) which has not been modified with boron, succinimide (C) modified with boron, a metallic detergent (D), and an antioxidant (E), wherein the ratio of the content of boron atoms derived from ingredient (C) to the content of nitrogen atoms derived from ingredients (B) and (C), B/N, is 0.30 or less by mass, the lubricating oil composition satisfying requirement (I) and/or requirement (II). Requirement (I): Ingredient (D) includes a metallic detergent (D1) having a base value less than 100 mgKOH/g. Requirement (II): Ingredient (E) includes an amine-based antioxidant (E1), the content of ingredient (E1) being 1.00 mass % or less.

A lubricating oil composition containing a base oil (A), a comb-shaped polymer (B), and an olefin-based copolymer (C), wherein a content of the component (B) is more than 0.80 mass % based on the total amount of the lubricating oil composition, a weight average molecular weight of the component (C) is 500,000 or more, and the lubricating oil composition has a viscosity index of 200 or more and a kinematic viscosity at 100° C. of 9.3 to 11.0 mm.sup.2/s.

The present application relates to the use of a lubricant composition comprising a base oil and a hydrogenated diene styrene polymer to reduce engine particulate emissions.

A lubricating composition comprises an oil-soluble poly(2-oxazoline) additive having the repeat unit:

—N(COR.sup.1)CH.sub.2CH.sub.2— where the number of repeat units (n) is an integer between 4 and 1000; where the polymer carries an inorganic or organic nucleophilic polymerization terminating group t, and a linear, branched or cyclic hydrocarbyl polymerization initiator group (i); and where R.sup.1 comprises a single or a mixture of linear branched or cyclic hydrocarbyl groups having 1-100 carbon atoms, some or all having 12-100 carbon atoms, or of at least one macro-monomeric hydrocarbyl group with more than 50 carbon atoms provided that when the polymer is a homopolymer and R.sup.1 lacks any hetero atoms; (A) i has a molecular weight of less than 250 g/mol, and R.sup.1 has an average number of carbon atoms of 12 to 50; or (B) n is greater than 15.

The polymer may provide the composition, in the form of a lubricant, with friction modifier, and with low impact on lubricant viscosity.

The polymer may be a homopolymer, a block copolymer or a star polymer.

The lubricating oil composition of the present invention contains, together with a base oil, a viscosity index improver (A) including a comb-shaped polymer (A1), a detergent dispersant (B) including an alkali metal borate (B1) and an organometallic compound (B2) containing a metal atom selected from an alkali metal atom and an alkaline earth metal atom, and a friction modifier (C) including a molybdenum-containing friction modifier, with the total content of an alkali metal atom and an alkaline earth metal atom being 2,000 mass ppm or less. The lubricating oil composition of the present invention has excellent detergency, fuel saving properties, and LSPI-preventing properties.

The present invention provides a poly(meth)acrylate-based viscosity index improver comprising a core portion and three or more arm portions, wherein each of the arm portions consists of a polymer chain comprising a structural unit represented by the following formula (1), and one end of the polymer chain is bonded to the core portion, and wherein a weight-average molecular weight Mw is 100000 or more, and a ratio of the weight-average molecular weight Mw to a number average molecular weight Mn, Mw/Mn, is 1.6 or less. ##STR00001## [R.sup.1 represents hydrogen or a methyl group, and R.sup.2 represents a C1 to C36 alkyl group.]

The present invention provides a process for preparing a polymer, employing the steps of: (1) contacting a free radical initiator; a chain transfer agent containing a thiocarbonyl thio group and a free radical leaving group; and a radically polymerizable monomer, to form a polymer chain; and (2) contacting the polymer chain of step (1) with at least one of a polyvalent coupling agent, a polymerization inhibitor, a grafting acylating agent, an amine and an oil of lubricating viscosity. The invention further provides compositions and uses for the polymer.

The invention provides a lubricating composition comprising a low viscosity base oil and a synergistic mixture of a functionalized ethylene-α-olefin copolymer, a poly(meth)acrylate polymer, and a metal-free anti-wear agent. The invention also provides a method of lubricating an internal combustion engine using such a lubricating composition.

The invention provides a lubricating composition comprising an oil of lubricating viscosity and synergistic mixture of a functionalized ethylene-α-olefin copolymer, a poly(meth)acrylate block polymer having a substantially oil soluble block and a substantially oil insoluble block. The invention also provides a method of lubricating a mechanical device using such a lubricating composition.

A lipophilic copolymer including polar multi-blocks having general formula (I):

[(B.sub.yA.sub.k).sub.s].sub.t(A.sub.jC.sub.m)  (I)

wherein: B represents at least one monomer unit deriving from a lipophilic monomer having general formula (II):

##STR00001## wherein: X represents a hydrogen atom; or a methyl group; R is selected from C.sub.1-C.sub.50 alkyl groups, linear or branched; A represents at least one monomer unit deriving from a polar monomer selected from: (a) compounds having general formula (III):

##STR00002## wherein X represents a hydrogen atom or a methyl group and n represents an integer comprised between 0 and 4; (b) (meth)acrylamide or (meth)acrylamides substituted on the nitrogen atom with one or two C.sub.1-C.sub.4 alkyl groups linear or branched; (c) di-(C.sub.1-C.sub.4)-alkylamino-(C.sub.1-C.sub.4)-alkyl (meth)acrylates; C represents at least one monomer unit deriving from a polar polyfunctional monomer having general formula (IV):

Z—(W).sub.p  (IV) wherein: Z represents a group containing carbon, hydrogen and, optionally, oxygen; and W represents a function able to react covalently with an alkyl radical.