The present disclosure relates to methods of improving viscosity shear stability of a lubricating oil and lubricating oil composition comprising: a base oil of lubricating viscosity; an amount of one or more zinc dialkyl dithiophosphate compound(s);
wherein the lubricating oil composition has one or both of the following ratios: a) a ratio of KV40° C..sub.fresh to a weight % of zinc contributed by the one or more zinc dialkyl dithiophosphate compound(s) based on a total weight of the lubricating oil composition, of greater than 510, wherein KV40° C..sub.fresh is the kinematic viscosity of the fresh lubricating oil composition at 40° C.; and b) a ratio of KV40° C..sub.fresh to a weight % of phosphorus contributed by the one or more zinc dialkyl dithiophosphate compound(s) based on a total weight of the lubricating oil composition, of greater than 560, wherein KV40° C..sub.fresh is the kinematic viscosity of the fresh lubricating oil composition at 40° C.

The present invention aims to provide a viscosity index improver composition and a lubricating oil composition having a low HTHS viscosity at 100° C., an excellent shear stability, and an excellent low temperature viscosity. The present invention relates to, for example, a viscosity index improver composition (C), containing: a copolymer (A) containing a polyolefin-based monomer (a) represented by the following formula (1) as a constituent monomer; a copolymer (B) containing a (meth)acrylic acid alkyl ester (c) having a C12-C15 straight-chain or branched alkyl group and a (meth)acrylic acid alkyl ester (d) having a C16-C20 straight-chain or branched alkyl group as constituent monomers; and a base oil, wherein a weight average molecular weight ratio {(A)/(B)} of the copolymer (A) to the copolymer (B) is 2 to 55, and a weight ratio (A/B) of the copolymer (A) to the copolymer (B) constituting the viscosity index improver composition (C) is 5 to 100: ##STR00001##

A lubricating oil composition includes an ethylene/α-olefin copolymer (A) having 70 to 90 mole % of structural units derived from ethylene and an intrinsic viscosity [η] of 0.3 to 1.0 dl/g.

A lubricating oil composition for a transmission, the composition including: (A) a lubricant base oil comprising a mineral base oil and/or a synthetic base oil; and (B) a poly(meth)acrylate having a weight average molecular weight of no more than 25,000, wherein the composition has a kinematic viscosity at 100° C. of 2.5 to 4.9 mm.sup.2/s.

The invention relates to the field of lubricants and provides a lubricating composition comprising at least one base oil, the kinematic viscosity of which measured at 40° C. does not exceed 10 mm.sup.2/s and the pour point of which does not exceed −50° C., and at least one thickener, said lubricating composition having a pour point not exceeding −55° C.

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.

An aspect of the present invention relates to a lubricant composition containing at least: (A) 50 to 80 mass % of silicone oil represented by formula (1) below, and having a mass-average molecular weight of 900 to 4000, a ratio (C/Si ratio) of carbon to silicon of 3.03 or higher in the structure, and a viscosity index (VI) of 300 or higher; (B) 10 to 49 mass % of hydrocarbon-based lubricant; and (C) 1 to 10 mass % of antioxidant.

A lubricating oil composition with a resin (A) and a base oil (B), the resin (A) is in a range of 0.01 to 50 parts by mass per 100 parts of (A) and (B), the resin (A) satisfies the following requirements: (A-1) the resin (A) is a polymer including a constituent unit from 4-methyl-1-pentene in a range of 60 to 99 mol % and a constituent unit from an α-olefin having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene) in a range of 1 to 40 mol % (provided that 4-methyl-1-pentene and the α-olefin is 100 mol %); (A-2) intrinsic viscosity [η] measured in decalin at 135° C. is in a range of 0.01 to 5.0 dl/g; (A-3) a melting point (Tm) is in a range of 110 to 150° C. as determined by DSC; and the base oil (B) has (B-1) kinematic viscosity at 100° C. is in a range of 1 to 50 mm.sup.2/s.

Described herein is a process, comprising: a) selecting an API Group II base stock with selected viscosity index and pour point; b) blending a base oil with the base stock, and c) adding to the base oil: i) a liquid ethylene propylene copolymer viscosity modifier that reduces a traction coefficient, and ii) an additive package, to make a driveline fluid that has a defined viscosity index and excellent shear stability. Also provided is a driveline fluid composition having the high viscosity index and excellent shear stability, comprising: a) a base oil comprising from 50 wt % to 100 wt % API Group II base stock; b) a liquid ethylene propylene copolymer viscosity modifier that reduces a traction coefficient; and c) an additive package. Further provided is a method for lubricating an axle or manual transmission by supplying the driveline fluid composition.

Described herein is a stabilized lubricant composition for use in steel casting, in particular in continuous casting processes. In particular, the lubricant composition for processes for producing steel by continuous casting includes a dispersion of a lubricant powder, for an ingot mold, in continuous casting, in an oily liquid means, and a stabilization additive, characterized in that it has the following shear thinning index values: TABLE-US-00001 RVT 0.1/1 1/10 10/100 100/1000 STI 3.0-7.5 2.0-6.5 1.0-3.0 0.5-2.0 wherein RVT is the ratio between two different shear speeds and STI is the shear thinning index corresponding to the RVT values.