Lubricant blend for gear oils including ev and DL fluids

Abstract

Lubricant fluids comprising about 10 wt% to about 99 wt% of a low-viscosity polyalpha-olefin (PAO), based on total weight of the lubricant fluid; wherein the low-viscosity PAO comprises about 10 mol% or less olefinic bonds, comprises about 90 wt% or greater C22-C32 polyalpha-olefins, and has a kinematic viscosity at 100°C (KV100), determined pursuant to ASTM D445, of about 1.5 cSt to about 15 cSt; optionally, about 0.1wt% to about 50 wt% of a high-viscosity base stock having a kinematic viscosity at 100°C (KV100), determined pursuant to ASTM D445, of about 40 cSt to about 2000 cSt; and about 1 wt% to about 50 wt% of a gear oil fluid additive package. Use of the lubricant fluids for lubrication and / or thermal management of surfaces in need thereof.

Description

LUBRICANT BLEND FOR GEAR OILS INCLUDING EV AND DL FLUIDSFIELD OF INVENTION

[0001] The present disclosure generally relates to lubricant fluids having improved properties, and more particularly, to lubricant fluids that may convey improved performance of gearbox, driveline, and electric drive units, such as reduction gears in electric vehicles.BACKGROUND

[0002] Electric vehicles are becoming increasingly more popular with consumers. Although there are some commonalities between electric vehicles and gasoline-powered vehicles, there are significant differences still in need of further technological development. For example, the fluids conventionally used for lubrication of internal combustion engines may not perform as well in electric vehicles. In some cases, conventional fluids may even be incompatible with the electric drive unit or other components of electric vehicles.

[0003] Electric vehicle drive units generally operate at much higher speeds and torque than internal combustion engine vehicles. In the case of a fluid used for lubrication of the electric motor, these differences may lead to increased wear of components and foammg / air entrainment within the fluid. Excessive air entrainment and / or insufficient wear protection may lead to decreased energy efficiency of an electric motor and / or hardware failure. For example, air entrainment may decrease lubricity and fluid pressure, and promote increased oxidative and thermal degradation. Decreased lubricity and fluid pressure may lead to increased system wear, especially at slow operating speeds. Poor heat dissipation can also decrease the operating efficiency of electric motors.

[0004] One or more of the same or similar considerations may apply to other applications, such as transmissions for internal combustion vehicles, axles, and gearboxes for vehicles and industrial equipment.

[0005] In view of the foregoing, there remains a need for fluids having improved performance for use as gear oils.SUMMARY OF INVENTION

[0006] In various aspects, methods of the present disclosure comprise: contacting a surface in need of lubrication and / or thermal management with a lubricant fluid comprising: about 10 wt% to about 99 wt% of a low-viscosity poly alpha-olefin (PAO), based on total weight of the lubricant fluid; wherein the low-viscosity' PAO comprises about 10 mol% or less olefinic bonds, comprises about 90 wt% or greater C22-C32 polyalpha-olefms, and has a kinematic viscosity at 100°C (KV 100), determined pursuant to ASTM D445, of about 1.5 cSt to about 15cSt; optionally, about 0.05 wt% to about 50 wt% of a high-viscosity' base stock having a KV100, determined pursuant to ASTM D445, of about 40 cSt to about 2000 cSt; an about 1 wt% to about 50 wt% of a gear oil additive package; wherein the lubricant fluid has: a change in KV100 (AKV100), determined pursuant to CEC-L-48 at 170°C, of no more than 40 cSt after 192 hours and no more than 200 cSt after 384 hours; a change in a kinematic viscosity' at 40°C (AKV40), determined pursuant to CEC-L-48 at 170°C, of no more than 40 cSt after 192 hours and no more than 200 cSt after 384 hours; a copper corrosion test change in electrical resistance in the oil phase of less than 50 kQ after 1000 hours at 150°C; a copper corrosion test change in electrical resistance in the vapor phase of less than 100 kQ after 1000 hours at 150°C; a mean coefficient of friction for boundary' lubrication, determined pursuant to FVA 345, of less than about 0.06 pmz at a relative film thickness ratio (X) between 0.02 and 0.1 and a pitch line velocity (vt) of 0.5 m / s; and a mean coefficient of friction for mixed lubrication or elastohydrodynamic (EHD) lubrication, determined pursuant to FVA 345, of less than about 0.035 pmz at a X between 0.1 and 0.7 and a vt of 8.3 m / s.

[0007] In various aspects, lubricant fluids of the present disclosure comprise: about 10 wt% to about 99 wt% of a low-viscosity polyalpha-olefm (PAO), based on total weight of the lubricant fluid; wherein the low-viscosity PAO comprises about 10 mol% or less olefinic bonds, comprises about 90 wt% or greater C22-C32 polyalpha-olefms, and has a kinematic viscosity at 100°C (KV100), determined pursuant to ASTM D445, of about 1.5 cSt to about 15 cSt; optionally, about 0.1 wt% to about 50 wt% of a high- viscosity base stock having a kinematic viscosity' at 100°C (KV100), determined pursuant to ASTM D445, of about 40 cSt to about 2000 cSt; and about 1 wt% to about 50 wt% of a gear oil fluid additive package; wherein the lubricant fluid has: a change in KV100 (AKV100), determined pursuant to CEC-L-48 at 170°C. of no more than 40 cSt after 192 hours and no more than 200 cSt after 384 hours; a change in a kinematic viscosity at 40°C (AKV40), determined pursuant to CEC-L-48 at 170°C, of no more than 40 cSt after 192 hours and no more than 200 cSt after 384 hours; a copper corrosion test change in electrical resistance in the oil phase of less than 50 kQ after 1000 hours at 150°C; and a copper corrosion test change in electrical resistance in the vapor phase of less than 100 kQ after 1000 hours at 150°C.

[0008] These and other features and attributes of the disclosed methods and systems of the present disclosure and their advantageous applications and / or uses will be apparent from the detailed description which follows.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] To assist those of ordinary skill in the relevant art in making and using the subject matter hereof, reference is made to the appended drawings. The following figures are included to illustrate certain aspects of the embodiments, and should not be viewed as exclusive configurations. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to those skilled in the art and having the benefit of this disclosure.

[0010] FIG. 1 presents the high pressure-viscosity -temperature dependency of base oils.

[0011] FIG. 2 graphs pmz(mean coefficient of friction) of two different formulated lubricants as a function of relative film thickness ratio A, under two different lubrication regimes (vt = 0.5 m / s and vt = 8.3 m / s).

[0012] FIG. 3 schematically depicts a copper corrosion test apparatus.

[0013] FIGS. 4A and 4B presents copper corrosion test results for a sample fluid and a comparative fluid.DETAILED DESCRIPTION

[0014] The present disclosure generally relates to lubricant fluids having improved properties, and more particularly, to lubricant fluids that may convey improved performance of mechanical systems, e.g., electric drive units, such as in electric vehicles, transmissions for internal combustion vehicles, axles, and gearboxes, such as in industrial systems.

[0015] In response to the foregoing issues, the present disclosure provides lubricant fluids containing polyalpha-olefins (PAOs) suitable for use in electric vehicles, among other applications. Advantageously, the lubricant fluids described herein may have improved oxidative stability relative to conventional lubricant fluids comprising blends of Group II and Group III base oils. The improved oxidative stability may enhance corrosion resistance of various metals in various components of electric drive units, such as the corrosion resistance of copper in electric motor windings. Also, the lubricant fluids descnbed herein may have a lower coefficient of friction under one or more of boundary, elastohydrodynamic, and mixed lubrication regimes relative to conventional lubricant fluids comprising blends of Group II and Group III base oils. The lower coefficient of friction may reduce torque loss and enhance energy efficiency of mechanical systems, such as electric drive units.

[0016] Lubricant fluids of the present disclosure may comprise: about 10 wt% to about 99 wt% of a low-viscosity polyalpha-olefin (PAO), based on total weight of the lubricant fluid, wherein the low-viscosity7PAO comprises about 10 mol% or less olefinic bonds and is a C22-C32 trimer of one or more C4-C12 linear alpha-olefins and has a kinematic viscosity at 100°C (KV100), determined pursuant to ASTM D445, of about 1.5 cSt to about 15 cSt; optionally.about 0.1 wt% to about 50 wt% of a high-viscosity base stock having a kinematic viscosity' at 100°C (KV100), determined pursuant to ASTM D445, of about 40 cSt to about 2000 cSt; and about 1 wt% to about 50 wt% of a gear oil fluid additive package; wherein the lubricant fluid has a change in KV100 (AKV100), determined pursuant to CEC-L-48 at 170°C, of no more than 40 cSt after 192 hours and no more than 200 cSt after 384 hours; a change in a kinematic viscosity at 40°C (AKV40), determined pursuant to CEC-L-48 at 170°C, of no more than 40 cSt after 192 hours and no more than 200 cSt after 384 hours; a mean coefficient of friction for boundary lubrication, determined pursuant to FVA 345, of less than about 0.06 pmzat a relative film thickness ratio (X) between 0.02 and 0.1 and a pitch line velocity' (vt) of 0.5 m / s; and a mean coefficient of friction for mixed lubrication or elastohydrodynamic (EHD) lubrication, determined pursuant to FVA 345, of less than about 0.035 pmzat aZ between 0.1 and 0.7 and a vt of 8.3 m / s. In accordance with the present disclosure, a surface in need of lubrication and / or thermal management, such as a surface of an electric drive unit, such as within an electric vehicle, may be contacted with the lubricant fluid in order to promote operation of the electric drive unit.

[0017] The term ”polyalpha-olefin(s)” (PAO(s)) includes any oligomer(s) and / or polymer(s) of one or more alpha-olefin monomer(s). Alpha-olefins have a terminal double bond on their carbon chain. PAOs may be produced from the polymerization reaction of alpha-olefin monomer molecules in the presence of a catalyst and optionally further hydrogenated to remove residual carbon-carbon double bonds (olefinic bonds) therefrom. PAOs may be dimers, trimers, tetramers, or even higher oligomers derived from one or more alpha-olefin monomers. The PAOs may be highly regio-regular such that the bulk material exhibits isotacticity' or syndiotacticity when assayed by13C NMR. Preferably, at least a majority7of the PAOs in the lubricant fluids is a trimer. The PAOs may be highly regio-irregular such that the bulk material is substantially atactic when assayed by13C NMR. In non-limiting examples, PAOs may be made using metallocene-based catalysts or traditional non-metallocene based catalysts (e.g., Lewis acids, supported chromium oxide, or the like).

[0018] The lubricant fluids may comprise about 10 wt% to about 99 wt% of a low-viscosity polyalpha-olefin (PAO), or about 85 wt% to about 95 wt%, or about 88 wt% to about 91 wt%, based on total weight of the lubricant fluid.

[0019] The PAOs may comprise olefinic bonds in an amount of about 10 mol % or less, or about 5 mol % or less, or about 3 mol % or less, or about 1 mol % or less, based on a total molar amount of the PAOs. Thus, the PAOs may be partially unsaturated or fully saturated PAOs. Preferably, the PAOs are substantially fully saturated. Any double bonds that do remainin the PAOs may include one or more of vinyl, disubstituted vinylene, trisubstituted vinylene, or vinylidene. The extent of unsaturation and amount of these types of double bonds may be determined by NMR spectroscopy, for example. The PAOs may contain a lurality of alkyl groups extending as side chains from the main backbone of the PAOs. The alkyl groups and the length thereof may be determined by the alpha olefins that undergo oligomerization to form the PAOs. In non-limiting examples, the alkyl groups may be, for instance, n-butyl. n-hexyl, n-octyl, n-decyl, n-dodecyl, or any combination thereof.

[0020] In non-limiting examples, the one or more PAOs may comprise C22-C32 PAOs at a total concentration of about 90 wt% or greater, or about 92 wt% or greater, or about 94 wt% or greater, or about 95 wt% or greater, or about 96 wt% or greater, or about 97 wt% or greater, or about 98 wt% or greater, based on total weight of the one or more PAOs. In some embodiments, the C22-C32 PAOs comprise C28-C32 PAOs. The C28-C32 PAOs may comprise trimers of one or more C4-C12 linear alpha olefins (LAOs).

[0021] In one or more embodiments, the one or more PAOs may comprise C30 PAOs at a total concentration of about 90 wt% or greater, or about 92 wt% or greater, or about 94 wt% or greater, or about 95 wt% or greater, or about 96 wt% or greater, or about 97 wt% or greater, or about 98 wt% or greater, based on total weight of the one or more PAOs. Fully saturated C30 PAOs may be represented by the formula C30H62, which may be a single alkane isomer or a mixture of multiple (e.g., two, three, four, or more) alkane isomers.

[0022] In non-limiting examples, the low- viscosity PAOs may comprise C22-C26, or C24- C26, or C22-C24 polyalpha-olefin oligomers at a total concentration of about 90 wt% or greater, or about 92 wt% or greater, or about 94 wt% or greater, or about 95 wt% or greater, or about 96 wt% or greater, or about 97 wt% or greater, or about 98 wt% or greater, based on total weight of the low-viscosity PAOs. Such low-viscosity PAOs may comprise C24 polyalphaolefin oligomers at a total concentration of about 90 wt% or greater, or about 92 wt% or greater, or about 94 wt% or greater, or about 95 wt% or greater, or about 96 wt% or greater, or about 97 wt% or greater, or about 98 wt% or greater, based on total weight of the low-viscosity' PAOs. Fully saturated C24 low-viscosity PAOs may be represented by the formula C24H50, which may be a single alkane isomer or a mixture of multiple (e.g., two, three, four, or more) alkane isomers.

[0023] The low viscosity' PAO may have a kinematic viscosity at 100°C (KV100), determined pursuant to ASTM D445, of about vl to about v2 cSt, where vl and v2 may be, independently, 1.0. 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7. 1.8, 1.9. 2.0, 2.1. 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 5.0, 5.5, 6.0,6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 11.0, 12.0. 13.0, 14.0, or 15.0, where vl and v2 are determined according to ASTM D445 and vl<v2. In non-limiting examples, vl is 3.0 and v2 is 4.0; or vl is 3.0 and v2 is 3.6; or vl is 3.0 and v2 is 3.5; or vl is 2.0 and v2 is 4.0; or vl is 1.5 and v2 is 15.

[0024] The low viscosity PAO may have viscosities of about psi to about ps2 Pa*s at pressures in a range of about pl to about p2 MPa, where psi and ps2 may be, independently, 7, 8, 9, 10, 20, 30, 40, 50, 75. 100, 200, 300, 400, 500, 600, 800. 1000. 1500, 2000, 2500, 3000, 3500, 4000, 4500, or 5000, with psi < ps2, and where pl and p2 may be, independently, 0, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, or 1500, with pl < p2. In some embodiments, pl is 900 and p2 is 1300. All values of pressure in this disclosure at which fluidity is maintained are determined using a falling body viscometer (Bair, “A Routine High-Pressure Viscometer for Accurate Measurements to 1 GPa,” Tribal Trans, 24(3):356-360 (2004)) with viscometer chamber rotation and a temperature of about 40°C, unless otherwise specified.

[0025] The low viscosity PAO may have a NV of about 15.0 wt% or less, or about 14.0 wt% or less, or about 13.0 wt% or less, or about 12.5 wt% or less, each determined pursuant to ASTM D5800.

[0026] The low viscosity PAO may have a thermal conductivity at 40°C of about 0.11 W (m C)'1to about 0.16 W (m °C)’1. All thermal conductivity values in this disclosure are determined according to ASTM D7896-19 and are reported in W (moC)_1, unless otherwise specified.

[0027] The low viscosity’ PAO may have a cold-cranking-simulator viscosity’ (CCSV) at -35°C of about al to about a2 centipoise (cP), where al and a2 may be, independently, 500, 550, 600, 650. 700, 750, 800, 850, 900, or 1000, provided that al is less than a2. All CCSV values in this disclosure are determined according to ASTM D5293 and are reported in cP (milliPascal second), unless otherwise specified.

[0028] The low viscosity PAO may have a high-temperature, high-shear viscosity (HTHSV) at 150°C of about 1.4 cP or less, such as about 1.0 cP to about 1.4 cP. or about 1.0 cP to about 1.3 cP, or about 1.0 cP to about 1.2 cP. All HTHSV values in this disclosure are determined according to ASTM D4683 and are reported in cP, unless otherwise specified.

[0029] The low viscosity PAO may have a high oxidation stability indicated by rotating pressure vessel oxidation test (RPVOT) break time of at least about 60 minutes, or at least about 70 minutes, or at least about 80 minutes. All RPVOT values in this disclosure are as determined according to ASTM D2272 and are reported in minutes, unless otherwise specified.

[0030] The lubricant fluids of the present disclosure may comprise about 0.1 wt% to about 50 wt% high-viscosity base stock, or about 1 wt% to about 10 wt% high- viscosity base stock, or about 2.5 wt% to about 12 wt% high viscosity base stock, such as about 4.5 wt% to about 5.5 wt% high viscosity base stock.

[0031] The high viscosity base stock may have a KV100, determined pursuant to ASTM D445, of at least about 20 cSt, such as from about 20 cSt to about 5000 cSt, or from about 30 cSt to about 3000 cSt, or from about 40 cSt to about 2000 cSt.

[0032] Examples of suitable high-viscosity polymer base stocks may include, but are not limited to, one or more of polyalpha-olefms, polyalkylmethacrylates (PAMAs), comb polymers (CP), comb polymer / PAMA mixed polymers, olefin copolymers (OCPs) such as ethylene-propylene copolymers (e.g.. EPM / EPDMs, such as LUCANT ethylene-propylene copolymers available from Mitsui), polyisobutylenes (PIBs), hydrogenated styrene-dienes (EISDs), re-refined base oils derived from any of the foregoing, and any combination thereof. SPECTRASYN ELITE 65, SPECTRASYN ELITE 150, SPECTRASYN ELITE 300, and SPECTRASYN 40, and SPECTRASYN 100 (all available from ExxonMobil) are examples of polyalpha-olefms that may be suitable as the high-viscosity polymer.

[0033] The lubricant fluids of the present disclosure may comprise from about 1 wt% to about 50 \vt% of gear oil fluid additive package, or from about 2.0 wt% to about 7.5 wt% of the gear oil additive package, or from about 4.5 wt% to about 6.5 wt% of the gear oil additive package.

[0034] Examples of gear oil additive packages include, but are not limited to, electrical vehicle (EV) fluid additive packages.

[0035] The lubricant fluids of the present disclosure may further comprise from about 3 wt% to about 50 wt% of a Group V base oil, or from about 5 wt% to about 50 wt% of the Group V base oil, or from about 5 wt% to about 25 wt% of the Group V base oil. The Group V base oil may comprise silicone, phosphate ester, polyalkylene glycol (PAG), ester, or any combination thereof. An ester may be a monoester, an adipate ester, a polyol ester, or any combination thereof, among others.

[0036] The lubricant fluids of the present disclosure may additionally include one or more anti-foam agents, such as, for example, silicones, polydimethyl siloxanes, acrylate ether copolymers, acrylate copolymers such as 2-ethylhexyl acrylate / vinyl acetate copolymer, fluorosilicone oils, and any combination thereof, among others. The anti-foaming agent(s) may be present in the lubricant fluids in a total amount of about 0.001 wt% to about 0.2 wt%, orabout 0.001 wt% to about 0.1 wt. %, or about 0.01 wt% to about 0.1 wt%, or about 0.05 wt% to about 0.15 wt%. based on total weight of the lubricant fluid.

[0037] The lubricant fluids of the present disclosure may additionally contain one or more additional components including but not limited to dispersants, detergents, anti -wear additives, corrosion inhibitors, rust inhibitors, metal deactivators, extreme pressure additives, anti-seizure agents, wax modifiers, fluid-loss additives, seal compatibility agents, lubricity agents, antistaining agents, chromophoric agents, de-emulsifiers, densifiers. wetting agents, gelling agents, tackiness agents, colorants, and others. Suitable examples of the foregoing and amounts commonly used will be familiar to persons having ordinary skill in the art. When lubricant fluids contain one or more of the components discussed above, the component(s) are blended into the lubricant fluid in an amount sufficient for the component(s) to perform its intended function.

[0038] One or more of anti-foam agents, dispersants, detergents, anti-wear additives, corrosion inhibitors, rust inhibitors, metal deactivators, extreme pressure additives, anti-seizure agents, wax modifiers, fluid-loss additives, seal compatibility agents, lubricity agents, antistaining agents, chromophoric agents, de-emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, and colorants may be included in a gear oil additive package, such as an EV fluid additive package.

[0039] It is noted that many of the foregoing additives are shipped from an additive manufacturer as a concentrate, sometimes containing one or more additives together, within a base oil diluent. For example, the base oil diluent may comprise about 5 wt% to about 50 wt% of the concentrate before blending to form a lubricant fluid. The additives useful in this disclosure do not necessarily have to be soluble in the lubricant fluids and instead may be present as dispersed solids.

[0040] The lubncant fluids may have a change in KV100 (AK.V100) in a range of about dl to d2 cSt, where dl and d2 may be, independently, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12,14, 16, 18, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or 200, with dl < d2. In some embodiments, dl is 0 and d2 is 40 after 192 hours. In some embodiments, dl is 0 and d2 is 200 after 384 hours. All AKV100 values in this disclosure are determined pursuant to CEC-L-48 at 170°C, unless otherwise specified.

[0041] The lubricant fluids may have a change in a kinematic viscosity at 40°C (AKV40) in a range of about el to e2 cSt, where el and e2 may be, independently, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12,14. 16, 18, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 120. 130, 140. 150, 160, 170, 180, 190, or 200, with el < e2. In some embodiments, el is 0 and e2 is 40 after 192hours. In some embodiments, el is 0 and e2 is 200 after 384 hours. All AKV40 values in this disclosure are determined pursuant to CEC-L-48 at 170°C, unless otherwise specified.

[0042] The lubricant fluids may have a copper corrosion test change in electrical resistance in the oil phase in a range of about ol to about o2 kQ. where ol and o2 may be, independently, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or 200, with ol < o2. In some embodiments, ol is 0 and o2 is 50. All values of copper corrosion test change in electrical resistance in the oil phase in this disclosure are determined pursuant to the copper corrosion test described in the Examples, unless otherwise specified.

[0043] The lubricant fluids may have a copper corrosion test change in electrical resistance in the vapor phase in a range of about gl to about g2 k , where gl and g2 may be, independently, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100. 110, 120, 130. 140, 150, 160. 170, 180, 190, or 200, with gl < g2. In some embodiments, gl is 0 and g2 is 100. All values of copper corrosion test change in electrical resistance in the oil phase in this disclosure are determined pursuant to the copper corrosion test described in the Examples, unless otherwise specified.

[0044] The lubricant fluids may have a KV 100 value in a range of about fl to 2 cSt, where fl and f2 may be, independently, 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10, with fl < f2. In some embodiments, fl is 4 and f2 is 5. All values of kinematic viscosity in this disclosure are determined pursuant to ASTM D445, unless otherwise specified.

[0045] The lubricant fluids may have a KV40 value in a range of about hl to h2 cSt, where hl and h2 may be, independently, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30, with hl < h2. In some embodiments, hl is 18 and h2 is 21.

[0046] The lubricant fluids may have a viscosity index (VI) value in a range of about il to about i2, where il and i2 may be, independently, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, or 240, where il < i2. In some embodiments, il is 140 and i2 is 160. All values of VI in this disclosure are determined pursuant to ASTM D2270, unless otherwise specified.

[0047] The lubricant fluids may have a pour point value in a range of about j 1 to j2 °C, wherein jl and j2 may be, independently, -120, -110, -100, -95, -90, -85, -80, -75, -70, -65, -60, -55, -50, -40, or -30, where jl <j2. In some embodiments, j 1 is -90 andj2 is -60. All pour point values in this disclosure are determined pursuant to ASTM D5950, unless otherwise specified.

[0048] The lubricant fluids may have a mean coefficient of friction for boundary lubrication in a range of about bl to about b2 pmz. where bl and b2 may be, independently, 0, 0.01, 0.02, 0.03, 0.04, 0.045, 0.05, 0.051, 0.052, 0.053, 0.054, 0.055, 0.056, 0.057, 0.058, 0.059, 0.06, 0.061, 0.062, 0.063, 0.064, 0.065, 0.066, 0.067, 0.068, 0.069, or 0.07 at a relative film thickness ratio (X) between 0.02 and 0.1 and a pitch line velocity (vt) of 0.5 m / s, with bl < b2. In some embodiments, bl is 0 and b2 is 0.06. In some embodiments, bl is 0.05 and b2 is 0.06. All values of mean coefficients of friction for boundary lubrication in this disclosure are determined pursuant to FVA 345, unless otherwise specified.

[0049] The lubricant fluids may have a mean coefficient of friction for mixed or elastohydrodynamic (EHD) lubrication in a range of about ml to about m2 pmz, where ml and m2 may be, independently. 0, 0.01. 0.015, 0.02, 0.021, 0.022, 0.023, 0.024, 0.025, 0.026, 0.026, 0.028, 0.029, 0.03, 0.031, 0.032, 0.033, 0.034, 0.035, 0.036, 0.037, 0.038, 0.039, or 0.04 at aZ between 0.1 and 0.7 and a vt of 8.3 m / s, with ml < m2. In some embodiments, ml is 0 and m2 is 0.035. In some embodiments, ml is 0.02 and m2 is 0.035. In some embodiments, ml is 0.02 and m2 is 0.028. All values of mean coefficients of friction for mixed lubrication and EHD lubrication in this disclosure are determined pursuant to FVA 345, unless otherwise specified.

[0050] The lubricant fluids may be used to lubricate surfaces of mechanical systems, such as electric drive units of electric vehicles. An electric drive unit may include an electric motor, a gearbox, one or more bearings, one or more gears, and optionally an axle. The type of electric motor is not particularly limited and may include one or more permanent magnets. The lubricant fluids may circulate through an electric motor or be sprayed onto electric motor or a component thereof to promote lubrication and thermal management. In non-limiting examples, the gearbox may be contacted with the lubricant fluids to reduce friction between one or more gears or another portion of the electric drive unit.

[0051] The lubricant fluids may be used to lubricate surfaces of other mechanical systems, such as transmissions of internal combustion vehicles, axles, and gearboxes for vehicles and industrial equipment. The lubricant fluids may circulate through a mechanical system or be sprayed onto a mechanical system or a component thereof to promote lubrication and / or thermal management. The lubricant fluids may be used for thermal management in nonmechanical systems, e.g., for thermal management in data centers.

[0052] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the present specification and associated claims are to be understood as being modified in all instances by the term “about.’’ Accordingly, unless indicated to the contrary, the numerical parameters setforth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the embodiments of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claim, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0053] One or more illustrative embodiments incorporating the invention embodiments disclosed herein are presented herein. Not all features of a physical implementation are described or shown in this application for the sake of clarity. It is understood that in the development of a physical embodiment incorporating the embodiments of the present invention, numerous implementation-specific decisions must be made to achieve the developer's goals, such as compliance with system-related, business-related, government-related and other constraints, which vary by implementation and from time to time. While a developer's efforts might be time-consuming, such efforts would be, nevertheless, a routine undertaking for those of ordinary skill in the art and having benefit of this disclosure.

[0054] While compositions and methods are described herein in terms of "‘comprising’' various components or steps, the compositions and methods can also “consist essentially of’ or “consist of’ the various components and steps.Additional Embodiments

[0055] The present disclosure is further directed to the following non-limiting embodiments:

[0056] Embodiment 1. A method comprising: contacting a surface in need of lubrication and / or thermal management with a lubricant fluid comprising: about 10 wt% to about 99 wt% of a low- viscosity polyalpha-olefin (PAO), based on total weight of the lubricant fluid; wherein the low- viscosity PAO comprises about 10 mol% or less olefinic bonds, comprises about 90 wt% or greater C22-C32 polyalpha-olefins, and has a kinematic viscosity at 100°C (KV100), determined pursuant to ASTM D445, of about 1.5 cSt to about 15 cSt; optionally, about 0.05 wt% to about 50 wt% of a high-viscosity base stock having a KV100, determined pursuant to ASTM D445, of about 40 cSt to about 2000 cSt; and about 1 wt% to about 50 wt% of a gear oil additive package; wherein the lubricant fluid has: a change in KV100 (AKV100), determined pursuant to CEC-L-48 at 170°C, of no more than 40 cSt after 192 hours and no more than 200 cSt after 384 hours; a change in a kinematic viscosity at 40°C (AKV40), determined pursuant to CEC-L-48 at 170°C, of no more than 40 cSt after 192 hours and no more than 200 cSt after 384 hours; a copper corrosion test change in electrical resistance in the oil phase of less than 50 k after 1000 hours at 150°C; a copper corrosion test change inelectrical resistance in the vapor phase of less than 100 k after 1000 hours at 150°C; a mean coefficient of friction for boundary lubrication, determined pursuant to FVA 345, of less than about 0.06 pmz at a relative film thickness ratio ( ) between 0.02 and 0.1 and a pitch line velocity (vt) of 0.5 m / s; and a mean coefficient of friction for mixed lubrication or elastohydrodynamic (EHD) lubrication, determined pursuant to FVA 345, of less than about 0.035 pmz at a X between 0.1 and 0.7 and a vt of 8.3 m / s.

[0057] Embodiment 2. The method of embodiment 1, wherein the lubricant fluid further has: a KV100, determined pursuant to ASTM D445, from about 4 cSt to about 5 cSt; a kinematic viscosity at 40°C (KV40), determined pursuant to ASTM D445, from about 18 cSt to about 21 cSt; a viscosity index (VI), determined pursuant to ASTM D2270, from about 140 to about 160; and a pour point, determined pursuant to ASTM D5950, from about -60°C to about -90°C.

[0058] Embodiment s. The method of embodiment 1 or embodiment 2, wherein the low-viscosity PAO has a viscosity of about 7 Pa.s to 5000 Pa.s at a pressure of 500 MPa or greater and a temperature of about 40°C.

[0059] Embodiment 4. The method of any one of embodiments 1 to 3, wherein the low-viscosity PAO comprises C28-C32 polyalpha-olefins at a concentration of about 95 wt% or greater, based on total weight of the PAO.

[0060] Embodiment s. The method of embodiment 4, wherein the low- viscosity PAO comprises C30 poly alpha-olefins at a concentration of about 95 wt% or greater, based on total weight of the PAO.

[0061] Embodiment 6. The method of any one of embodiments 1 to 3, wherein the low-viscosity polyalpha-olefin comprises C24 polyalpha-olefm oligomers at a concentration of about 95 wt% or greater, based on total weight of the low- viscosity polyalpha-olefin.

[0062] Embodiment 7. The method of any one of embodiments 1 to 5, wherein the lubricant fluid comprises from about 85 wt% to about 95 wt% of the low-viscosity PAO, from about 2.5 wt% to about 12 wt% of the high viscosity base stock, and from about 2.0 wt% to about 7.5 wt% of the gear oil additive package , each based on total weight of the lubricant fluid.

[0063] Embodiment 8. The method of any one of embodiments 1 to 7, wherein the lubricant fluid further comprises an anti-foam agent.

[0064] Embodiment 9. The method of embodiment 8, wherein the lubricant fluid comprises from about 0.001 wt% to about 0.2 wt% of the anti-foam agent, based on total weight of the lubricant fluid.

[0065] Embodiment 10. The method of any one of embodiments 1 to 9, wherein the lubricant fluid comprises from about 88 wt% to about 91 wt% of the low-viscosity PAO, from about 4.5 wt% to about 5.5 wt% of the high viscosity base stock, and from about 4.5 wt% to about 6.5 wt% of the gear oil fluid additive package, each based on total weight of the lubricant fluid.

[0066] Embodiment 11. The method of any one of embodiments 1 to 10, wherein the lubricant fluid further comprises from about 3 wt% to about 50 wt% of a Group V base oil.

[0067] Embodiment 12. The method of any one of embodiments 1 to 11, wherein the surface is a surface of an electric drive unit in need of lubrication.

[0068] Embodiment 13. The method of embodiment 12, wherein the electric drive unit comprises an electric motor, one or more bearings, and a gearbox.

[0069] Embodiment 14. The method of embodiment 13, wherein the electric drive unit further comprises at least one permanent magnet.

[0070] Embodiment 15. The method of any one of embodiments 1 to 14, wherein the surface is in need of thermal management.

[0071] Embodiment 16. A lubricant fluid, comprising: about 10 wt% to about 99 wt% of a low-viscosity polyalpha-olefin (PAO), based on total weight of the lubricant fluid; wherein the low- viscosity PAO comprises about 10 mol% or less olefinic bonds, comprises about 90 wt% or greater C22-C32 polyalpha-olefins, and has a kinematic viscosity at 100°C (KV100), determined pursuant to ASTM D445, of about 1.5 cSt to about 15 cSt; optionally, about 0.1 wt% to about 50 wt% of a high-viscosity base stock having a kinematic viscosity at 100°C (KV100), determined pursuant to ASTM D445, of about 40 cSt to about 2000 cSt; and about 1 wt% to about 50 wt% of a gear oil fluid additive package; wherein the lubricant fluid has: a change in KV100 (AKV100), determined pursuant to CEC-L-48 at 170°C, of no more than 40 cSt after 192 hours and no more than 200 cSt after 384 hours; a change in a kinematic viscosity at 40°C (AKV40), determined pursuant to CEC-L-48 at 170°C, of no more than 40 cSt after 192 hours and no more than 200 cSt after 384 hours; a copper corrosion test change in electrical resistance in the oil phase of less than 50 kQ after 1000 hours at 150°C; and a copper corrosion test change in electrical resistance in the vapor phase of less than 100 k after 1000 hours at 150°C.

[0072] Embodiment 17. The lubricant fluid of embodiment 16, wherein the lubricant fluid further has: a KV100, determined pursuant to ASTM D445, from about 4 cSt to about 5 cSt; a kinematic viscosity at 40°C (KV40), determined pursuant to ASTM D445, from about 18 cSt to about 21 cSt; a viscosity index (VI), determined pursuant to ASTM D2270, fromabout 140 to about 160; and a pour point, determined pursuant to ASTM D5950, from about -60°C to about -90°C.

[0073] Embodiment 18. The lubricant fluid of embodiment 16 or embodiment 17, wherein the low-viscosity PAO further has a viscosity of about 7 Pa.s to 5000 Pa.s at a pressure of 500 MPa or greater and a temperature of about 40°C.

[0074] Embodiment 19. The lubricant fluid of any one of embodiments 16 to 18, wherein the low-viscosity PAO comprises C28-C32 polyalpha-olefins at a concentration of about 95 wt% or greater, based on total weight of the PAO.

[0075] Embodiment 20. The lubricant fluid of embodiment 19, wherein the low- viscosity PAO comprises C30 polyalpha-olefins at a concentration of about 95 wt% or greater, based on total weight of the PAO.

[0076] Embodiment 21. The lubricant fluid of any one of embodiments 16 to 18, wherein the low-viscosity polyalpha-olefin comprises C24 polyalpha-olefin oligomers at a concentration of about 95 wt% or greater, based on total weight of the low-viscosity polyalphaolefin.

[0077] Embodiment 22. The lubricant fluid of any one of embodiments 16 to 21, wherein the lubricant fluid comprises from about 85 wt% to about 95 wt% of the low-viscosity PAO, from about 2.5 wt% to about 12 wt% of the high viscosity base stock, and from about 2.0 wt% to about 7.5 wt% of the gear oil fluid additive package , each based on total weight of the lubricant fluid.

[0078] Embodiment 23. The lubricant fluid of any one of embodiments 16 to 22, wherein the lubricant fluid further comprises from about 3 wt% to about 50 wt% of a Group V base oil.

[0079] Embodiment 24. The lubricant fluid of any one of embodiments 16 to 23, wherein the lubricant fluid further comprises an anti-foam agent.

[0080] Embodiment 25. The lubricant fluid of embodiment 24, wherein the lubricant fluid comprises from about 0.001 wt% to about 0.2 wt% of the anti-foam agent, based on total weight of the lubricant fluid.

[0081] Embodiment 26. The lubricant fluid of any one of embodiments 16 to 25, wherein the lubricant fluid comprises from about 88 wt% to about 91 wt% of the low-viscosity PAO, from about 4.5 wt% to about 5.5 wt% of the high viscosity7base stock, and from about 4.5 wt% to about 6.5 wt% of the gear oil fluid additive package, each based on total weight of the lubricant fluid.

[0082] To facilitate a better understanding of the embodiments of the present invention, the following examples of preferred or representative embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the invention.EXAMPLES

[0083] Properties of exemplary7base oils were evaluated, the compositions of which are specified in Table 1 below.Table 1Ultra-Low Low Group II Group III Group II Group III Viscosity ViscosityPAO PAO C28-32Sample 1 Sample 2 Cl C2 C3 C4 KV100 °C2.335 3.509 2.698 4.112 2.993 4.219 (cSt)KV40 °C8.21 14.24 9.84 18.35 11.95 19.23 (cSt)VI96 128 113 127 104 126 Flash Point203 225 201 - 199 230 (°C)Pour Point<-60 <-60 -49 -42 -37 -15 (°C)0084] High pressure viscosity of base oils. Samples 1-2 and C1-C4 were subjected to high pressure viscosity testing in a falling body viscometer (Bair, "‘A Routine High-Pressure Viscometer for Accurate Measurements to 1 GPa,” Tribal Trans, 24(3):356-360 (2004)) with viscometer chamber rotation and a temperature of 40°C. Pressures ranged from about 150 MPa to about 1250 MPa.

[0085] Results of the high pressure viscosity testing are shown in FIG. 1. None of Comparative Examples C1-C4 had viscosity7that could be measured throughout the entire pressure range. The last data point for each series (Cl and C3, about 800 MPa; C2, about 675 MPa; C4, about 350 MPa) is the pressure beyond which the sinker in the falling body viscometer stopped moving. This suggests all of C1-C4 underwent a phase transition at pressures from about 400 MPa to about 900 MPa, which suggests that lubricant fluids predominantly comprising any of C1-C4 could be prone to greater wear or mechanical failure of lubricated components.

[0086] In contrast. Samples 1-2 had measurable viscosity (e.g.. from about 7 Pa.s to 5000 Pa s) at a pressure of 500 MPa or greater, e.g. up to the maximum tested pressure of about 1250MPa. Samples 1-2 also had smaller viscosity increases with increasing pressure relative to C2-C4.

[0087] Improved energy efficiency of lubricants. Fully formulated lubricants were prepared comprising Sample 2 from Table 1 (Experimental Fluid 1) or Group II / III base oils (Comparative Fluid 1), as set forth in Table 2.Table 2Experimental Comparative Component Fluid 1 Fluid 1 Sample 2 88%(Gr III) 44% Additive package fortransmission / driveline 12% 12% fluid(Gr II) 44% Total 100% 100% UnitProperty7Method Data Kinematic Viscosity @cSt ASTM D445 4.174 4.027 100°CKinematic Viscosity (a} 40°C cSt ASTM D445 18.14 17.48 NoViscosity Index ASTM D2270 137 132 unitPour Point °C ASTM D5950 -78 -66 Brookfield Viscosity @- cP ASTM D2983 2,148 3846 40°CNoack Volatility, ASTM D5800,wt% 11.58 25.25evaporation loss (250C) Procedure B

[0088] The mean coefficient of friction pmzof Experimental Fluid 1 and Comparative Fluid 1 were tested according to the FZG test of FVA 345. using A pe C gears with pc= 1350 N / mm2FIG. 2 graphs pmzas a function of relative film thickness ratio Z for both Experimental Fluid 1 and Comparative Fluid 1 under both the boundary lubrication regime (vt = 0.5 m / s) and the mixed lubrication or elastohydrodynamic (EHD) lubrication regime (vt = 8.3 m / s). Under both lubrication regimes, at any compared value of X. Experimental Fluid 1 had a lower value of pmzthan Comparative Fluid 1. A lower coefficient of friction of an automotive or industrial lubricant fluid may lead to improved energy efficiency or fuel economy.

[0089] Lubricant fluids comprising Sample 2. Properties of exemplary' lubricant fluids were evaluated, the compositions of which are specified in Table 3 below. The lubricant fluids consisted of one or more base oils and a fixed amount of high viscosity base stock and an electric vehicle (EV) additive package. Experimental Fluid 2 was formulated with Sample 2from Table 1. Comparative Fluid 2 was formulated with a blend of Group II and Group III base oils.Table 3Component Experimental Fluid 2 Comparative Fluid 2Sample 2 89.50% 0.00%Group II base stock 0.00% 53.50%Group III base stock 0.00% 36.00%High Viscosity base stock 5.00% 5.00%EV additive package 5.50% 5.50%

[0090] Selected properties of Experimental Fluid 2 and Comparative Fluid 2 are specified in Table 4 below.Table 4Component Experimental Fluid 2 Comparative Fluid 2KV100 (cSt) 4.534 4.512KV40 (cSt) 19.67 20.49VI 150.9 137.3Pour Point (°C) -75 -24

[0091] Copper Corrosion Testing. Experimental Fluid 2 and Comparative Fluid 2 were subjected to copper corrosion testing. Briefly, as depicted in FIG. 3 two separate copper wires 112, 114 are wound around a polytetrafluoroethylene (PTFE) stand 116 (diameter 30 mm, height 110 mm) placed in a liquid-tight controlled-temperature chamber 100. The wires 112, 114 are held in place near the middle of the stand 116 and the fluid under test is poured around the stand such that one wire 112 is immersed in the candidate fluid 120 and the other wire 114 is suspended in the vapor phase 130. The vapor phase 130 comprises air at the beginning of the test. During the course of the test, volatile organic compounds in the candidate fluid 120 are expected to enter the vapor phase 130. The chamber 100, including the stand 116, both copper wires 112, 114, and the fluid 120 under test, is heated to 150 °C for 1000 h. During the test, an electrical current (maximum 1 mA) flows through the wires 112, 114 and the electrical resistance of the wires 112, 114 is monitored over time.

[0092] Results for both Experimental Fluid 2 and Comparative Fluid 2 are shown in FIG.4A (oil phase) and FIG. 4B (vapor phase). For Comparative Fluid 2, the resistance of the oilphase wire reached about 3332 kQ (maximum detection limit) after about 400 hours runtime. The resistance of the vapor-phase wire reached the maximum detection limit after about 980 hours runtime. Visual inspection of the test wires showed significant corrosion.

[0093] In contrast, the oil-phase wire immersed in Experimental Fluid 2 showed no significant increase (< 50 kQ) in resistance over the life of the test and the vapor- phase wire reached a maximum resistance of only about 50 kQ (after circa 270 hours runtime). Visual inspection of the test wi res showed minimal corrosion.

[0094] Oxidative Stability Testing. Experimental Fluid 2 and Comparative Fluid 2 were also subjected to oxidative stability testing according to CEC-L-48 at 170°C for 192 hours and 384 hours.

[0095] After 192 hours, Comparative Fluid 2 showed large values of AKV40 (about +90 cSt) and AKV100 (about +80 cSt). Even larger values of AKV40 and AKV100 were observed after 384 hours (about +290 cSt and about +220 cSt, respectively).

[0096] Experimental Fluid 2 also showed positive values of AK.V40 and AKV100, but the overall increases were much smaller than were observed for Comparative Fluid 2. Specifically, after 192 hours, Experimental Fluid 2 had a AKV40 value of about +32 cSt and a AKV100 value of about +29 cSt. Even after 384 hours, Experimental Fluid 2 had a AKV40 value of about +165 cSt and a AKV100 value of about +130 cSt. These results indicate that Experimental Fluid 2 had better oxidative stability than Comparative Fluid 2. Though not to be bound by theory, the better oxidative stability may at least in part explain the superior performance of Experimental Fluid 2 in the copper corrosion test.

[0097] Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present invention. The invention illustratively disclosed herein suitably may be practiced in the absence of any element that is not specifically disclosed herein and / or any optional element disclosed herein. While compositions and methods are described in terms of ‘'comprising,” '‘containing,” or ‘'including”various components or steps, the compositions and methods can also “consist essentially of’ or “consist of’ the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or. equivalently, “from approximately a-b'’) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a’' or “an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces.

Claims

CLAIMSThe invention claimed is:

1. A lubricant fluid, comprising:about 10 wt% to about 99 wt% of a low-viscosity polyalpha-olefin (PAO), based on total weight of the lubricant fluid; wherein the low-viscosity PAO comprises about 10 mol% or less olefinic bonds, comprises about 90 wt% or greater C22-C32 polyalpha-olefins, and has a kinematic viscosity' at 100°C (KV 100), determined pursuant to ASTM D445, of about 1.5 cSt to about 15 cSt;optionally, about 0. lwt% to about 50 wt% of a high-viscosity base stock having a kinematic viscosity at 100°C (KV100), determined pursuant to ASTM D445. of about 40 cSt to about 2000 cSt; andabout 1 wt% to about 50 wt% of a gear oil fluid additive package;wherein the lubricant fluid has:a change in KV100 (AKV100), determined pursuant to CEC-L-48 at 170°C, of no more than 40 cSt after 192 hours and no more than 200 cSt after 384 hours;a change in a kinematic viscosity' at 40°C (AKV40), determined pursuant to CEC-L-48 at 170°C, of no more than 40 cSt after 192 hours and no more than 200 cSt after 384 hours;a copper corrosion test change in electrical resistance in the oil phase of less than 50 kQ after 1000 hours at 150°C;a copper corrosion test change in electrical resistance in the vapor phase of less than 100 k after 1000 hours at 150°C;a mean coefficient of friction for boundary lubrication, determined pursuant to FVA 345, of less than about 0.06 pmzat a relative film thickness ratio ( ) between 0.02 and 0.1 and a pitch line velocity (vt) of 0.5 m / s; and,a mean coefficient of friction for mixed lubrication or elastohydrodynamic (EHD) lubrication, determined pursuant to FVA 345, of less than about 0.035 pmzat a between 0.1 and 0.7 and a vt of 8.3 m / s.

2. The lubricant fluid of claim 1, wherein the lubricant fluid further has:a KV100, determined pursuant to ASTM D445, from about 4 cSt to about 5 cSt; a kinematic viscosity at 40°C (KV40), determined pursuant to ASTM D445, from about 18 cSt to about 21 cSt;a viscosity index (VI), determined pursuant to ASTM D2270, from about 140 to about 160; anda pour point, determined pursuant to ASTM D5950, from about -60°C to about -90°C.

3. The lubricant fluid of any preceding claim, wherein the low-viscosity PAO further has a viscosity of about 7 Pa.s to 5000 Pa.s at a pressure of 500 MPa or greater and a temperature of about 40°C.

4. The lubricant fluid of any preceding claim, wherein the low-viscosity PAO comprises C28-C32 polyalpha-olefins at a concentration of about 95 wt% or greater, based on total weight of the PAO.

5. The lubricant fluid of any preceding claim, wherein the low-viscosity PAO comprises C30 polyalpha-olefins at a concentration of about 95 wt% or greater, based on total weight of the PAO.

6. The lubricant fluid of any preceding claim, wherein the low-viscosity7polyalphaolefin comprises C24 poly alpha-olefin oligomers at a concentration of about 95 wt% or greater, based on total weight of the low-viscosity poly alpha-olefin.

7. The lubricant fluid of any preceding claim, wherein the lubricant fluid comprises from about 85 wt% to about 95 wt% of the low-viscosity PAO, from about 2.5 wt% to about 12 wt% of the high viscosity base stock, and from about 2.0 wt% to about 7.5 wt% of the gear oil fluid additive package, each based on total weight of the lubricant fluid.

8. The lubricant fluid of any preceding claim, wherein the lubricant fluid further comprises from about 3 wt% to about 50 wt% of a Group V base oil.

9. The lubricant fluid of any preceding claim, wherein the lubricant fluid comprises from about 88 wt% to about 91 wt% of the low-viscosity PAO, from about 4.5 wt% to about 5.5 wt% of the high viscosity7base stock, and from about 4.5 wt% to about 6.5 wt% of the gear oil fluid additive package, each based on total weight of the lubricant fluid.

10. A method comprising:contacting a surface in need of lubrication and / or thermal management with the lubricant fluid of any of claims 1-9:

11. The method of claim 10, wherein the lubricant fluid further comprises from about 0.001 wt% to about 0.2 wt% of the anti-foam agent, based on total weight of the lubricant fluid.

12. The method of claim 10 or 11, wherein the surface is a surface of an electric drive unit in need of lubrication.

13. The method of claim 12, wherein the electric drive unit comprises an electric motor, one or more bearings, and a gearbox.

14. The method of claim 13, wherein the electric drive unit further comprises at least one permanent magnet.

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