Patent Description:
The present disclosure generally relates to a lubricant composition.

Lubricant compositions are typically required to have a number of performance characteristics associated with the lubricant composition itself and/or with the performance of the equipment in which the lubricant composition is to be used (e.g. vehicles). Recently, market forces and governmental regulations have placed a renewed emphasis on fuel efficiency for vehicles. <CIT> describes a synthetic lubricant based on polyalkylene glycols. Thus, there remains an opportunity to develop a lubricant composition with improved fuel efficiency.

The present disclosure provides a lubricant composition. The lubricant composition includes a polyalkylene glycol base oil component in an amount of at least about <NUM> parts by weight based on <NUM> parts by weight of the lubricant composition. The lubricant composition has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt and a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt, each measured in accordance with ASTM D445. The lubricant composition is useful for increasing the fuel efficiency of a vehicle.

The present disclosure provides a lubricant composition. The lubricant composition can be utilized in a variety of lubricating applications, and is especially useful as a lubricant for axles.

The lubricant composition includes a polyalkylene glycol base oil component. Typically, the polyalkylene glycol base oil component includes two, three, four, or more polyalkylene glycols.

In certain embodiments, the lubricant composition includes the polyalkylene glycol base oil component from about <NUM> to about <NUM> parts by weight based on <NUM> parts by weight of the polyalkylene glycol base oil component. Alternatively, the lubricant composition includes the polyalkylene glycol base oil component in an amount of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, parts by weight based on <NUM> parts by weight of the lubricant composition. Alternatively, the lubricant composition includes the polyalkylene glycol base oil component in an amount of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, parts by weight based on <NUM> parts by weight of the lubricant composition.

The lubricant composition has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt when measured in accordance with ASTM D445. It is to be understood that for the purpose of this disclosure, any reference to kinematic viscosity is the kinematic viscosity as measured by ASTM D445. In certain embodiments, the lubricant composition has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, cSt.

The lubricant composition also has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt. In certain embodiments, the lubricant composition has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, cSt. In other embodiments, the lubricant composition has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, cSt.

The lubricant composition has a viscosity index of from about <NUM> to about <NUM> as measured in accordance with ASTM D2270. Alternatively, the lubricant composition may have a viscosity index of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>. It is to be understood that for the purpose of this disclosure, any reference to viscosity index is the viscosity index as measured by ASTM D2270.

The kinematic viscosity and the viscosity index of the lubricant composition results in the lubricant composition being particularly useful for lubricating an axle of a vehicle, such that the lubricant composition may also be referred to as an axle lubricant. Similarly, the kinematic viscosity and the viscosity index of the lubricant composition results in the lubricant composition being particularly useful for lubricating transmissions (manual or automatic), transfer cases, transaxles, power take off (PTO), and bearings/wheels. In addition, persons of skill in the art will also appreciate that the kinematic viscosity of the lubricant composition may make the lubricant composition unsuitable for some applications, such as rotary screw compressor lubricants.

In certain embodiments, the lubricant composition is essentially free of Type I, II, III, and IV base oils, as classified according to the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. In the context of this disclosure, "essentially free of Type I, II, III, and IV base oils" means that the lubricant composition includes less than a combined total of about <NUM> parts by weight of Type I, II, III, and IV base oils, based on <NUM> parts by weight of the lubricant composition. Alternatively, "essentially free of Type I, II, III, and IV base oils" means that the lubricant composition includes less than a combined total of about <NUM>, about <NUM>, about <NUM>, or about <NUM>, parts by weight of Type I, II, III, and IV base oils, based on <NUM> parts by weight of the lubricant composition. As one example, the lubricant composition may still be essentially free of Type I, II, III, and IV base oils and contain about <NUM> parts by weight of one or more of these oils when one of the additives (described further below) included in the lubricant composition is dispersed in a Type I, II, III, and/or IV base oil.

Referring back to the polyalkylene glycol base oil component, the polyalkylene glycol base oil component is water-insoluble. In these embodiments with the water-insoluble polyalkylene glycol base oil component, the polyalkylene glycol base oil component includes a polyalkylene glycol A and a fourth polyalkylene glycol B. Generally, both the polyalkylene glycols A and B are homopolymers formed from the reaction product of propylene oxide. Because the polyalkylene glycols A and B are homopolymers formed from the reaction product of propylene oxide, the polyalkylene glycols A and B are typically considered to be water-insoluble. The terms "A" and "B" are terms of convenience utilized to distinguish the polyalkylene glycols in the water-insoluble embodiments from the polyalkylene glycols utilized in the comparative, water-soluble embodiments.

Typically, the polyalkylene glycol A has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt and a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt. Similarly, the polyalkylene glycol B has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt and a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt. In general, the polyalkylene glycol B has a kinematic viscosity that is greater than the kinematic viscosity of the polyalkylene glycol A at <NUM> and <NUM>. In these embodiments, the blend of the polyalkylene glycols A and B typically establish the kinematic viscosity and viscosity index of the lubricant composition as described above.

In certain embodiments, the polyalkylene glycol A has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, cSt.

In certain embodiments, the polyalkylene glycol A has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, cSt.

In certain embodiments, the polyalkylene glycol B has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, cSt.

In certain embodiments, the polyalkylene glycol B has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, cSt.

In one embodiment, the polyalkylene glycol A has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt and a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt. In addition, the polyalkylene glycol B has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt and a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt.

Although not required, the lubricant composition may include the polyalkylene glycol A in an amount of from about <NUM> to about <NUM> parts by weight based on <NUM> parts by weight of the lubricant composition. Alternatively, the lubricant composition may include the polyalkylene glycol A in an amount of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, parts by weight based on <NUM> parts by weight of the lubricant composition.

The lubricant composition may further include the polyalkylene glycol B in an amount of from about <NUM> to about <NUM> parts by weight based on <NUM> parts by weight of the lubricant composition. Alternatively, the lubricant composition may include the polyalkylene glycol B in an amount of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, parts by weight based on <NUM> parts by weight of the lubricant composition.

In embodiments when the polyalkylene glycol base oil component is water-insoluble, the lubricant composition further includes an ester base oil being a diester. In addition to being a base oil, the ester base oil being a diester may also dissolve and/or disperse the additive package (described further below). Typically, the ester being a diester is formed from, dicarboxylic acids, or polycarboxlyic acids with one or more alcohols. Generally, the alcohols are C1 to C18 alcohols and may be either linear or branched. Suitable alcohols include, but are not limited to, butanol, hexanol, dodecanol, <NUM>-ethylhexanol, and propylheptanol. Specific examples of the ester base oil being a diester that is included in the lubricant composition include, but are not limited to, dibutyl adipate, di(<NUM>-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate didecyl phthalate, dieicosyl sebacate, the <NUM>-ethylhexyl diester of linoleic acid dimer, and the dipropylheptanol diester of adipic acid.

The lubricant composition includes the ester being a diester typically in an amount of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, parts by weight based on <NUM> parts by weight of the lubricant composition.

In one embodiment, the lubricant composition includes a dipropylheptanol diester of adipic acid in an amount of from about <NUM> to about <NUM> parts by weight, the polyalkylene glycol A in an amount of from about <NUM> to about <NUM> parts by weight, and the polyalkylene glycol B in an amount of from about <NUM> to about <NUM> parts by weight, each based on <NUM> parts by weight of the lubricant composition. In this embodiment, the polyalkylene glycol A has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt and a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt. In addition, the polyalkylene glycol B has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt and a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt. Moreover, in this embodiment, both the polyalkylene glycols A and B are homopolymers formed from propylene oxide. Moreover, in this embodiment, the lubricant composition is generally used to lubricant an axle, transmissions (manual or automatic), transfer cases, transaxles, power take off (PTO), and/or bearings/wheels of a vehicle while achieving increased fuel efficiency for the vehicle. Without being held to any particular theory, it is believed that the combination of the polyalkylene glycols A and B produce the increased fuel efficiency. More specifically, it is believed that the combination of the chemistry and the kinematic viscosity of the blend of the polyalkylene glycols A and B impart excellent low and high temperature properties to the lubricant composition, which increases the fuel efficiency of the lubricant composition when the lubricant composition is used to lubricate the above referenced components of the vehicle.

In certain embodiments, the lubricant composition exhibits improved fuel efficiency in comparison to conventional lubricants. This increased fuel efficiency can be observed when the lubricant composition is analyzed with a Minimum Traction Machine (MTM) under Stribeck conditions and Slide-Roll Ratio (SRR) at <NUM> and <NUM>. In certain embodiments, the lubricant composition has a traction coefficient of less than <NUM> when measured under Stribeck conditions, at a speed of <NUM>,<NUM>/s, and at a temperature of <NUM>. Without being bound to any particular theory, it is believed that the amount of the polyalkylene glycol base oil component and its kinematic viscosity at <NUM> and <NUM> produces a lubricant composition having improved fuel efficiency. In particular it is believed that polyalkylene glycol base oil component imparts excellent low and high temperature properties to the lubricant composition, which increases the fuel efficiency of the lubricant composition when the lubricant composition is used to lubricate an axle, transmissions (manual or automatic), transfer cases, transaxles, power take off (PTO), and/or bearings/wheels of a vehicle. This increased fuel efficiency is demonstrated by the traction coefficients of the lubricant composition described above. In addition, despite demonstrating increased fuel efficiency, the lubricant composition also has good shear stability and oxidation resistance, among other properties. Moreover, the lubricant composition also allows exhibits improved (i.e., lower) operating temperatures in comparison to conventional lubricants due to the fact that heat generated from friction is minimized as evidenced by the comparatively lower traction coefficient.

The lubricating composition may also include an additive package. The additive package includes at least one additive effective to improve at least one property of the lubricant composition and/or the performance of the equipment in which the lubricant composition is to be used. In certain embodiments, the additive package includes one or more additives chosen from antioxidants, corrosion inhibitors, foam control additives, extreme pressure additives, anti-wear additives, detergents, metal passivators, pour point depressant, and viscosity index improvers. Although not required, the additive package and the lubricant composition are generally essentially free of dispersants. In certain embodiments, the additive package, or a portion of the additive package, is commercially available from Afton Chemical under the tradename HITEC® <NUM>.

It is to be appreciated that the individual additives included in the additive package may be combined with one or more other additives prior to being added to the lubricant composition, or in the alternative, the individual additives may be separately added to the lubricant composition. In other words, the additive package does not require that all, or even a portion, of the additives be combined prior to being combined with the polyalkylene glycol base oil component.

When the lubricant composition includes the additive package, the additive package is typically present in an amount of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, parts by weight based on <NUM> parts by weight of the lubricant composition.

In regards to the anti-wear additive, any anti-wear additive known in the art may be included. Suitable, non-limiting examples of the anti-wear additive include zinc dialkyl-dithio phosphate ("ZDDP"), zinc dialkyl-dithio phosphates, sulfur- and/or phosphorus- and/or halogen-containing compounds, e.g. sulfurised olefins and vegetable oils, zinc dialkyldithiophosphates, alkylated triphenyl phosphates, tritolyl phosphate, tricresyl phosphate, chlorinated paraffins, alkyl and aryl di- and trisulfides, amine salts of mono- and dialkyl phosphates, amine salts of methylphosphonic acid, diethanolaminomethyltolyltriazole, bis(<NUM>-ethylhexyl)aminomethyltolyltriazole, derivatives of <NUM>,<NUM>-dimercapto-<NUM>,<NUM>,<NUM>-thiadiazole, ethyl <NUM>-[(diisopropoxyphosphinothioyl)thio]propionate, triphenyl thiophosphate (triphenylphosphorothioate), tris(alkylphenyl) phosphorothioate and mixtures thereof (for example tris(isononylphenyl) phosphorothioate), diphenyl monononylphenyl phosphorothioate, isobutylphenyl diphenyl phosphorothioate, the dodecylamine salt of <NUM>-hydroxy-<NUM>,<NUM>-thiaphosphetane <NUM>-oxide, trithiophosphoric acid <NUM>,<NUM>,<NUM>-tris[isooctyl <NUM>-acetate], derivatives of <NUM>-mercaptobenzothiazole such as <NUM>-[N,N-bis (<NUM>-ethylhexyl)aminomethyl]-<NUM>-mercapto-<NUM>-<NUM>,<NUM>-benzothiazole, ethoxycarbonyl-<NUM>-octyldithio carbamate, ashless anti-wear additives including phosphorous, and/or combinations thereof. In one embodiment, the anti-wear additive is ZDDP.

If included, the anti-wear additive may be included in the lubricant composition in an amount of from about <NUM> to about <NUM>, alternatively from about <NUM> to about <NUM>, alternatively from about <NUM> to about <NUM>, alternatively from about <NUM> to about <NUM>, alternatively from about <NUM> to about <NUM>, alternatively from about <NUM> to about <NUM>, alternatively from about <NUM> to about <NUM>, parts by weight based on <NUM> parts by weight of the lubricant composition. The amount of anti-wear additive may vary outside of the ranges above, but is typically both whole and fractional values within these ranges. Further, it is to be appreciated that more than one anti-wear additive may be included in the lubricant composition, in which case the total amount of all the anti-wear additive included is within the above ranges. Further, it is to be appreciated that more than anti-wear additive may be included in the lubricant composition, in which case the total amount of all the anti-wear additives included is within the above ranges.

Similarly, any pour point depressant known in the art may be included. The pour point depressant is typically selected from polymethacrylate and alkylated naphthalene derivatives, and combinations thereof.

If included, the pour point depressant may be included in the lubricant composition in an amount of from about <NUM> to about <NUM>, alternatively from about <NUM> to about <NUM>, alternatively from about <NUM> to about <NUM>, alternatively from about <NUM> to about <NUM>, parts by weight based on <NUM> parts by weight of the lubricant composition. The amount of pour point depressant may vary outside of the ranges above, but is typically both whole and fractional values within these ranges. Further, it is to be appreciated that more than one pour point depressant may be included in the lubricant composition, in which case the total amount of all the pour point depressant included is within the above ranges.

In regards to the antifoam agent, any antifoam agent known in the art may be included. The antifoam agent is typically selected from silicone antifoam agents, acrylate copolymer antifoam agents, and combinations thereof.

If included, the antifoam agent may be included in the lubricant composition in an amount of from about <NUM> to about <NUM>, alternatively from about <NUM> to about <NUM>, alternatively from about <NUM> to about <NUM>, ppm based on the total weight of the lubricant composition. The amount of antifoam agent may vary outside of the ranges above, but is typically both whole and fractional values within these ranges. Further, it is to be appreciated that more than one antifoam agent may be included in the lubricant composition, in which case the total amount of all the antifoam agent included is within the above ranges.

If included, the detergent is typically selected from overbased or neutral metal sulfonates, phenates and salicylates, and combinations thereof. For example, in various embodiments, the detergent is selected from metal sulfonates, phenates, salicylates, carboxylates, thiophosphonates, and combinations thereof. In one embodiment, the detergent includes an overbased metal sulfonate, such as calcium sulfonate. In another embodiment, the detergent includes an overbased metal salicylate, such as calcium metal salicylate. In yet another embodiment, the detergent includes an alkyl phenate detergent.

If employed, the detergent may be included in the lubricant composition in an amount of from about <NUM> to about <NUM>, alternatively of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, parts by weight based on <NUM> parts by weight of the lubricant composition. The amount of detergent may vary outside of the ranges above, but is typically both whole and fractional values within these ranges. Further, it is to be appreciated that more than one detergent may be included in the lubricant composition, in which case the total amount of all the detergent included is within the above ranges.

If employed, the viscosity index improver can be of various types. Suitable examples of viscosity index improvers include polyacrylates, polymethacrylates, vinylpyrrolidone/methacrylate copolymers, polyvinylpyrrolidones, polybutenes, olefin copolymers, styrene/acrylate copolymers and polyethers, and combinations thereof.

If employed, the viscosity index improver can be used in various amounts. The viscosity index improver may be present in the lubricant composition in an amount of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, parts by weight based on <NUM> parts by weight of the lubricant composition. The amount of viscosity index improver may vary outside of the ranges above, but is typically both whole and fractional values within these ranges. Further, it is to be appreciated that more than one viscosity index improver may be included in the lubricant composition, in which case the total amount of all the viscosity index improver included is within the above ranges.

If employed, the antioxidant can be of various types. Suitable antioxidants include alkylated monophenols, alkylthiomethylphenols, hydroquinones and alkylated hydroquinones, hydroxylated thiodiphenyl ethers, alkylidenebisphenols, O-, N- and S-benzyl compounds, hydroxybenzylated malonates, triazine compounds, aromatic hydroxybenzyl compounds, benzylphosphonates, acylaminophenols, Esters of [<NUM>-(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl)propionic acid with mono- or polyhydric alcohols, esters of β-(<NUM>-tert-butyl-<NUM>-hydroxy-<NUM>-methylphenyl)-propionic acid with mono- or polyhydric alcohols, aminic antioxidants, aliphatic or aromatic phosphites, esters of thiodipropionic acid or of thiodiacetic acid, salts of dithiocarbamic or dithiophosphoric acid, <NUM> sulfurized fatty esters, sulfurized fats and sulfurized olefins, and combinations thereof, may be used.

If included, the antioxidant can be used in various amounts. The antioxidant is typically present in the lubricant composition in an amount ranging of from about <NUM> to about <NUM>, of from about <NUM> to about <NUM>, or of from about <NUM> to about <NUM>, parts by weight based on <NUM> parts by weight of the lubricant composition.

The present disclosure also provides a method of increasing the fuel efficiency of a vehicle having an axle. The method includes providing the lubricant composition. The method further includes contacting the lubricant composition with the axle of the vehicle to increase the fuel efficiency of the vehicle.

The present disclosure also provides a method of increasing the fuel efficiency of a vehicle having an axle. The method includes providing the lubricant composition. The method further includes contacting the lubricant composition with at least one component of the vehicle chosen from the group of transmissions (manual or automatic), transfer cases, transaxles, power take offs, bearings/wheels, and combinations thereof to increase the fuel efficiency of the vehicle.

In one embodiment, the method of the disclosure includes providing the axle lubricant to increase the fuel efficiency of a vehicle having an axle. In this embodiment, the polyalkylene glycol base oil component of the axle lubricant is present in an amount of at least about <NUM> parts by weight based on <NUM> parts by weight of the axle lubricant. In addition, the axle lubricant has a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt and a kinematic viscosity at <NUM> of from about <NUM> to about <NUM> cSt. Moreover, the axle lubricant also has a traction coefficient of less than <NUM> when measured under Stribeck conditions, at a speed of <NUM>,<NUM>/s, and at a temperature of <NUM>. The method further includes contacting the lubricant and the axle of the vehicle with the axle lubricant to increase the fuel efficiency of the vehicle.

Two lubricant compositions are provided in Table <NUM> as Lubricant Compositions <NUM> (comparative only) and <NUM> (inventive). Table <NUM> also provides two comparative lubricants as Comparative Lubricants A and B. Each individual component for each lubricant in Table <NUM> is provided in parts by weight based on <NUM> parts by weight of the respective lubricant.

Base Oil <NUM> is a water-soluble copolymer of ethylene oxide and propylene oxide, having a kinematic viscosity at <NUM> of about <NUM> to about <NUM> cSt and a kinematic viscosity at <NUM> of about <NUM> to about <NUM> cSt.

Base Oil <NUM> is a water-soluble copolymer of ethylene oxide and propylene oxide, having a kinematic viscosity at <NUM> of about <NUM> to about <NUM> cSt and a kinematic viscosity at <NUM> of about <NUM> to about <NUM>,<NUM> cSt.

Base Oil <NUM> is a water-insoluble homopolymer of propylene oxide, having a kinematic viscosity at <NUM> of about <NUM> to about <NUM> cSt and a kinematic viscosity at <NUM> of about <NUM> to about <NUM> cSt.

Base oil <NUM> is a diester of <NUM>-propylheptanol and adipic acid.

Base oil <NUM> is a group I base oil commercially available from ExxonMobil under the tradename Americas CORE <NUM>™.

Base oil <NUM> is a polyalphaolefin base oil commercially available from ExxonMobil having a kinematic viscosity at <NUM> of <NUM> cSt.

The kinematic viscosity and viscosity index of Lubricant Compositions <NUM>(comparative) -<NUM> (inventive) and Comparative Lubricants A-B were measured and are also provided in Table <NUM>.

The traction coefficient were measured with a MTM under Stribeck conditions, at a temperature of <NUM> and also at a temperature of <NUM>. The results at <NUM> and <NUM> are provided in <FIG>, respectively.

The results demonstrate that Lubricant Compositions <NUM> (comparative) and <NUM> (inventive) have excellent fuel efficiency.

Two additional lubricant compositions are provided in Table <NUM> as Lubricant Compositions <NUM> (comparative) and <NUM> (inventive). Also provided in Table <NUM> is a comparative lubricant as Comparative Lubricant C. Each individual component for each lubricant is provided in parts by weight based on <NUM> parts by weight of the respective composition.

Base oils <NUM>-<NUM> and <NUM> are as described above.

Base oil <NUM> is a metallocene catalyzed polyalphaolefin base oil commercially available from ExxonMobil having a kinematic viscosity at <NUM> of <NUM> cSt.

The performance additives include the performance additives described above.

Physical properties of Lubricant Compositions <NUM> (comparative) - <NUM> (inventive), and Comparative Lubricant C are also provided in Table <NUM>.

The traction coefficients for Lubricant Compositions <NUM> (comparative) - <NUM> (inventive), Comparative Lubricant C, and Emgard <NUM> were measured under Stribeck conditions and Slide-Roll conditions. Emgard <NUM> is a commercially available lubricant and was included for the purpose of providing an additional Comparative Lubricant. First, the traction coefficients were measured with a MTM under Stribeck conditions, at a temperature of <NUM>. The results for this first traction coefficient test at <NUM> are provided in <FIG>. Second, the traction coefficients were measured with a MTM under Slide-Roll ratio conditions and at a temperature of <NUM>. The results for this second traction coefficient test are provided in <FIG>. As shown in <FIG>, Lubricant Compositions <NUM> (comparative) and <NUM> (inventive) have excellent fuel efficiency.

Claim 1:
A lubricant composition comprising a polyalkylene glycol base oil component in an amount of at least <NUM> parts by weight based on <NUM> parts by weight of said lubricant composition, wherein said lubricant composition has a kinematic viscosity at <NUM> of from <NUM> to <NUM> cSt and a kinematic viscosity at <NUM> of from <NUM> to <NUM> cSt, each measured in accordance with ASTM D445,
wherein said polyalkylene glycol base oil component comprises:
a polyalkylene glycol A being a homopolymer formed from propylene oxide and having a kinematic viscosity at <NUM> of from <NUM> to <NUM> cSt and a kinematic viscosity at <NUM> of from <NUM> to <NUM> cSt, each measured in accordance with ASTM D445, and
a polyalkylene glycol B being a homopolymer formed from propylene oxide and having a kinematic viscosity at <NUM> of from <NUM> to <NUM> cSt and a kinematic viscosity at <NUM> of from <NUM> to <NUM> cSt, each measured in accordance with ASTM D445,
wherein said polyalkylene glycol B has a kinematic viscosity that is greater than the kinematic viscosity of said polyalkylene glycol A at <NUM> and <NUM>
wherein said polyalkylene glycol base oil component is water-insoluble,
wherein said polyalkylene glycol base oil component comprises:
said polyalkylene glycol A in an amount of from <NUM> to <NUM> parts by weight based on <NUM> parts by weight of said polyalkylene glycol base oil component, and
said polyalkylene glycol B in an amount of from <NUM> to <NUM> parts by weight based on <NUM> parts by weight of said polyalkylene glycol base oil component,
the lubricant composition having a viscosity index of from <NUM> to <NUM> as measured in accordance with ASTM D2270 and further comprising a diester.