PRESSURE PERFORMANCE

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to lubricant formulations having a hydrocarbon base oil with oil soluble polyalkylene glycol, sulfurized olefin and phosphate ester additives.

Introduction

Automotive axel oil lubricants typically contain 70-95 weight-percent (wt%) base oil 0-15 wt% viscosity index improvers, up to 2 wt% pour point depressants and 2-30 wt% of a detergent inhibitor (DI) package. The DI package contains additives such as extreme pressure (EP) additives, anti-wear (AW) additives, dispersants, anti-oxidants, corrosion inhibitors, friction modifiers and foam inhibitors. The additives in the DI package are generally required to meet performance requirements.

EP additives generally include sulfur-containing species. Sulfur is an effective EP additive because it forms a sacrificial tribofilm of iron sulfide with a metal surface. The iron sulfide film is displaced upon shock thereby protecting the metal surface. Dispersants are used to disperse resulting iron sulfide particles. Anti-wear (AW) additives are also surface active and can form films on the metal surface to reduce wear between contacting surfaces. Typical AW additives contain phosphorous. The phosphorous also tries to bind with the metal surface to protect it from extreme wear. When both sulfur-containing EP and phosphorous-containing AW additives are present there is a competition between the sulfur and phosphorous for the metal surface. As a result, efficacy of one or both EP and AW additive can diminish when both are present.

It is desirable to identify a lubricant formulation that achieves improved AW performance without sacrificing EP performance while still using standard sulfur-containing EP additives and phosphorous-containing AW additives.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a solution to the problem of identifying a lubricant formulation that achieves improved AW performance without sacrificing EP performance while still using standard sulfur-containing EP additives and phosphorous-containing AW additives. Moreover, the present invention provides a way to improve both AW and EP performance at a given concentration of sulfur-containing EP additive and phosphorous- containing AW additive.

The present invention is a result of a surprising and unexpected discovery that oil soluble polyalkylene glycol (OSP) when added to a lubricant formulation comprising a hydrocarbon base oil, sulfur-containing EP additive and a phosphorous-containing AW additive increases the EP and AW performance of the formulation. The OSP surprisingly and unexpectedly synergistically enhances the performance of both additives in the oil formulation.

In a first aspect, the present invention is a lubricant formulation comprising: (a) greater than 50 weight-percent hydrocarbon base oil; (b) 5 weight-percent or more and less than 50 weight-percent of one or a combination of more than one oil soluble polyalkylene glycol selected from a group consisting of monol, diol and triol initiated 1 ,2-butylene oxide homopolymers and monol initiated copolymers of 1,2-butylene oxide and propylene oxide; (c) 0.1 weight-percent or more and 5 weight-percent or less of sulfurized olefin in one embodiment and 0.1 weight-percent or more and 3 weight-percent or less of sulfurized olefin in another embodiment; and (d) 0.1 weight-percent or more and 2 weight-percent or less of phosphate ester in one embodiment and 0.1 weight-percent or more and 1.5 weight- percent or less of phosphate in another embodiment; where weight-percent is relative to total lubricant formulation weight.

In a second aspect, the present invention is a method of increasing anti-wear performance without reducing extreme pressure performance of a lubricant formulation containing a hydrocarbon base oil, a sulfurized isobutylene extreme pressure additive and a phosphate ester anti-wear additive, the method comprising including an oil soluble polyalkylene glycol selected from a group consisting of monol, diol and triol initiated

1,2-butylene oxide homopolymers and monol initiated copolymers of 1,2-butylene oxide and propylene oxide into the lubricant formulation so as to obtain the lubricant formulation of the first aspect.

The formulation and method of the present invention is useful as a lubricant.

The oil soluble polyalkylene glycols of the present invention can be designed from oxides other than 1,2 butylene oxide. For example it is possible to design oil soluble polyalkylene glycols from other higher oxides such as hexene oxide, octene oxide, dodecene oxide or styrene oxide such that homo-polymers are produced by reacting the oxides with an initiator such as an alcohol. Alternatively, copolymers can be produced by reacting mixtures of the copolymers with an initiator. Alternatively, mixtures of a higher oxide and 1,2 propylene oxide or 1,2 butylene oxide can be used to prepare copolymers. The above alternative types of oil soluble polyalkylene glycols are expected to provide a similar technical effect as the copolymers of propylene oxide and butylene oxide or homo-polymers of butylene oxide that are described herein in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

"And/or" means "and, or alternatively". All ranges include endpoints unless otherwise stated. Weight-percent (wt%) is relative to total lubricant formulation weight unless otherwise stated.

Test methods refer to the most recent test method as of the priority date of this document unless a date is indicated with the test method number as a hyphenated two digit number. References to test methods contain both a reference to the testing society and the test method number. Test method organizations are referenced by one of the following abbreviations: ASTM refers to ASTM International (formerly known as American Society for Testing and Materials); EN refers to European Norm; DIN refers to Deutsches Institut fur Normung; and ISO refers to International Organization for Standards.

Determine kinematic viscosity according to ASTM D7042. Determine viscosity index for a lubricant composition according to ASTM D2270. Determine pour point temperature according to ASTM D97.

Determine molecular weight for non-capped oil soluble polyalkylene glycol polymers in grams per mole (g/mol) from the OH (hydroxyl) number according to ASTM D4274. Determine the molecular weight for capped oil soluble polyalkylene glycol polymers by adding the weight of the capping agent minus one. For example, the molecular weight of a methyl capping group is 15, but since the methyl group is chemically replacing a hydrogen on the non-capped polyalkylene glycol the resulting molecular weight of the polyalkylene glycol is increased by 15 from the capping group but reduced by one from loss of the hydrogen that is replaced.

Characterize extreme pressure (EP) performance using a pin and vee-block test according to ASTM D3233. The test is the "Falex EP test". The test apparatus is available from Falex Corporation and consists of a 0.25 inch (6.35 millimeter) diameter steel rod (journal) that rotates at 290 +/- 10 revolutions per minute against two 0.5 inch (12.7 millimeter) diameter vee blocks. A four line contact region is established as load is applied through a mechanical sprint-type gage by a ratchet wheel and an eccentric arm. The test determines a load-fail value that relates to the load-carrying properties of the test fluid. The Falex load gage applies from 200 to 3000 pounds (91-1361 kilograms) direct load (4500 pounds (2041 kilograms) reference load). Conduct the test against test method B until a rise in friction coefficients or a drop in load or a failure of the shear pin is observed. A typical automotive gear oil formulation that contains extreme pressure additives will have a load carrying capacity of 2500 pounds (1135 kilograms) while a typical engine oil formulation that does not contain sulfur based extreme pressure additives has a load carrying capacity of 1300 pounds (590 kilograms). An "increase" and an "improvement" in extreme pressure performance, and an "increased", "improved", and/or "higher" extreme pressure performance, each corresponds to an increase in load carrying capacity.

Characterize anti-wear (AW) performance using the ASTM D4172 4-ball wear test run at 100°C. Anti-wear values are in millimeters (mm). Higher values correspond to greater wear and poorer anti-wear performance. Lower values correspond to better anti- wear performance. Therefore, a decrease in anti-wear performance characterization value corresponds to an "improvement" in anti-wear performance and an "increased",

"improved", and/or "higher" anti-wear performance.

The lubricant formulation comprises a natural or synthetic hydrocarbon base oil.

Hydrocarbon base oils are classified by the American Petroleum Institute (API) into five classes: Group I, Group II, Group ΠΙ, Group IV and Group V. Group Ι-ΙΠ base oils are considered natural hydrocarbon base oils, Group IV base oils are synthetic hydrocarbon base oils that are polyalphaolefins and Group V base oils are considered other synthetic base oils. Group I base oils are composed of fractionally distilled petroleum which is further refined with solvent extraction processes to improve properties such as oxidation resistance and to remove wax. The viscosity index of Group I base oils is between 80 and 120. Group I base oils have a sulfur content of more than 0.03 weight percent (wt%). Group II base oils are composed of fractionally distilled petroleum that has been hydrocracked to further refine and purify it. Group Π base oils also have a viscosity index between 80 and 120, but a sulfur content of less than 0.03 wt%. Group ΙΠ base oils have similar characteristics to Group II base oils but have a viscosity index above 120 with a sulfur content less than 0.03 wt%. Group II base oils are highly hydro-processed oils and Group III base oils are highly hydro- cracked oils. Group ΙΠ base oils have a higher viscosity index than Group II base oils, and are prepared by either further hydro-cracking of Group II base oils, or by hydro-cracking of hydro-isomerized slack wax, which is a byproduct of the dewaxing process used for many of the oils in general. Group IV base oils are synthetic hydrocarbon oils, which are also referred to as polyalphaolefins (PAOs). Group V base oils are other synthetic base oils such as synthetic esters, polyalkylene glycols, polyisobutylenes, and phosphate esters. The hydrocarbon base oil for use in the present invention can be selected from any of Group I, II, ΙΠ or rv base oils or any combination selected thereof. In one desirable embodiment, the hydrocarbon base oil is selected form Group ΠΙ and rv base oils.

The hydrocarbon base oil is present at a concentration of greater than 50 weight- percent (wt%), preferably 55 wt% or more, more preferably 60 wt% or more and can be 65 wt% or more, 70 wt% or more, 75 wt% or more, 80 wt% or more, 85 wt% or more, even 90 wt% or more relative to the total weight of the lubricant formulation.

The inventive lubricant formulation also comprises an oil soluble polyalkylene glycol (OSP). OSPs are miscible, preferably soluble, in hydrocarbon base oils as is evident by their ability to form a clear mixture as evaluated optically with an unaided eye.

Polyalkylene glycols (PAGs) that comprise polymerized alkylene oxides selected only from ethylene oxide and propylene oxide are not considered OSPs. Desirably, the lubricant formulation of the present invention is free of PAGs that comprise polymerized alkylene oxides selected only from ethylene oxide and propylene oxide and can be free of PAGs that are not OSPs. PAGs generally comprise an initiator component, a polyalkylene oxide component and an end group at the end of each polyalkylene oxide chain opposite from the initiator component.

The OSP of the present lubricant formulation is selected from a group consisting of monol, diol and triol initiated 1,2-butylene oxide homopolymers and monol initiated copolymers of 1,2-butylene oxide and 1,2-propylene oxide (herein referred to simply as "propylene oxide"). Preferably the 1,2-butylene oxide homopolymer is monol or diol initiated, and most preferably monol initiated. Monols, diols and triols are alcohols having from one to 18 carbon atoms, preferably having six or more, more preferably eight or more and still more preferably ten or more carbon atoms while at the same time preferably having 16 or fewer, more preferably 14 or fewer and most preferably 12 or fewer carbon atoms. Monols are alcohols with a single hydroxyl group. Diols are alcohols with two hydroxyl groups. Triols are alcohols with three hydroxyl groups. Examples of desirable monol initiators include 1-dodecanol, butanol, octanol, 2-ethylhexanol, decanol, and oleyl alcohol. Examples of suitable diols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, and 1 ,4-butanediol. Examples of suitable triols include glycerol and

trimethylolpropane.

The 1 ,2-butylene oxide homopolymer is initiated with a monol, diol or triol and contains polymerized 1,2-butylene oxide as its only polyalkylene oxide component. The copolymer of 1,2-butylene oxide and propylene oxide is imitated with a monol and contains copolymerized 1,2-butylene oxide and propylene oxide as its only polyalkylene oxide component. The copolymerized 1 ,2-butylene oxide and propylene oxide can be block or randomly copolymerized, but is preferably randomly polymerized to form a random copolymer. The OSP that is a copolymer of 1,2-butylene oxide and propylene oxide desirably is made using 50 wt% or more 1,2-butylene oxide relative to total weight of 1,2-butylene oxide and propylene oxide.

The OSP can be capped or remain uncapped. If the OSP remains uncapped, it terminates with a hydroxyl group (-OH) on the end opposite from the alcohol initiator for each alkylene oxide polymer chain extending from the alcohol initiator. Desirably, the OSP remains uncapped. It can, however, be capped with groups such as alkyl, aryl and alkylaryl groups.

One example of a desirable OSP is an uncapped dodecanol-initiated random copolymer of 1,2-butylene oxide and propylene oxide. Desirably, the weight ratio of 1,2-butylene oxide and propylene oxide is approximately 50:50. Alternatively, or additionally, the copolymer has a molecular weight of 300 grams per mole (g/mol) or more, preferably 400 g/mol or more, more preferably 450 g/mol or more and most preferably 500 g/mol or more while at the same time has a molecular weight of 700 g/mol or less, preferably 600 g/mole or less, more preferably 550 g/mol or less and most preferably 500 g/mol or less.

The OSP is present at a concentration of 5 wt% or more, preferably 10 wt% or more and can be present at a concentration of 15 wt% or more, 20 wt% or more, 25 wt% or more, even 30 wt% or more. At the same time, the OSP is typically present at a concentration of 50 wt% or less. The lubricant formulation of the present invention further comprises a sulfurized olefin. The sulfurized olefin serves as an extreme pressure additive and is desirably selected from those sulfurized olefins known to serve as extreme pressure additives in lubricant formulations. Sulfurized olefins are generally prepared by initially reacting sulfur and an alkali-metal sulfide hydrate such as sodium sulfide nonahydrate in a high pressure reactor to form a sulfur-sulfide as taught, for example, in US5135670, which is incorporated herein by reference. An olefin is then added and the mixture stirred and heated. The sulfurized olefin is then recovered, washed with water and dried . The olefin in the sulfurized olefin is desirably selected from olefins having from 2 to 32 carbons atoms such as, for example, butylenes, pentenes, propenes. Desirably, the olefin is isobutylene. The mole ratio between sulfur plus sulfide and olefin generally ranges from 5:1 to 1: 1.

The concentration of sulfurized olefin in the lubricant formulation is desirably 0.1 wt% or more, preferably 0.5 wt% or more, more preferably one wt% or more, and can be 1.5 wt% or more. At the same time, the concentration of sulfurized olefin in the lubricant formulation is typically 5 wt% or less and can be 3 wt% or less, 2.5 wt% or less, 2 wt% or less and even 1.5 wt% or less.

The lubricant formulation further comprises a phosphate ester. The phosphate ester typically serves as an anti-wear additive in the formulation. The phosphate ester can be selected from two classes of materials: esters of alcohols and esters of phenols. The phosphate ester has a general formula of 0=P(OR)3 where each R is independently selected from a group consisting of hydrogen, alkyl, aryl and alkyl aryl groups preferably provided that at least one R is not hydrogen. The phosphate ester can be a reaction product of phosphoryl chloride and alcohols or phenols. Examples of suitable phosphate esters are trixylenylphosphate and tributylphenylphosphate. The phosphate ester can also be an acid phosphate which is a reaction product of an alcohol or phenol with phosphorous pentoxide. Acid phosphates have the structure of 0=P(OR)3 where one or two of the R groups are hydrogen.

The phosphate ester is typically present at a concentration of 0.1 wt% or more, and 2 wt% or less, or 1.5 wt% or less based on total weight of the lubricant formulation.

Desirably, the phosphate ester is present at a concentration of 0.25 wt% or more, preferably 0.5 wt% or more, more preferably 0.75 wt% or more, even more preferably one wt% or more and can be present at a concentration of 1.2 wt% or more while at the same time is desirably present at a concentration of less than 2 wt%, and can be at a concentration of less than 1.5 wt%, and can be present at a concentration of 1.4 wt% or less, 1.3 wt% or less, 1.2 wt% or less, 1.1 wt% or less, and even one wt% or less where wt% is relative to total weight of the lubricant formulation.

Particularly desirable formulations of the present invention comprise a combination of hydrocarbon oil selected from Group I, II, ΙΠ and IV base oils, dodecanol-initiated random copolymer of 1,2-butylene oxide and propylene oxide, sulfurized isobutylene and a phosphate ester.

The lubricant formulation can contain components in addition to the hydrocarbon base oil, OSP, sulfurized olefin and phosphate ester. For example, the lubricant formulation can contain additional additives commonly used in lubricant formulations. Examples of suitable additional components include any one or combination of more than one selected from a group consisting of antioxidants, corrosion inhibitors, anti-wear additive, foam control agents, yellow metal passivators, dispersants, detergents, friction reducing agents, pour point depressants and dyes. Additional additives are desirably soluble in the hydrocarbon base oil.

The lubricant formulation of the present invention surprisingly achieves increased anti-wear performance without sacrificing, and often while increasing, extreme pressure performance while still using standard sulfur-containing EP additive sand phosphorous- containing AW additive relative to a similar formulation without either the AW additive or without the OSP. The OSP, sulfurized olefin and phosphate ester unexpectedly operate synergistically to increase extreme pressure performance of the lubricant formulation.

Accordingly, the present invention further includes a method for increasing the AW performance of a lubricant formulation containing hydrocarbon base oil, sulfurized olefin and phosphate ester without decreasing (and often while increasing) the EP performance of the formulation. The method comprises including in the lubricant formulation an OSP selected from a group consisting of alcohol initiated homopolymers of 1 ,2-butylene oxide and alcohol-initiated random copolymers of 1 ,2-butylene oxide and propylene oxide into the lubricant formulation so as to obtain the lubricant of the present invention as described herein. The alcohol initiator is desirably selected from monols and diols for the

1,2-butylene oxide homopolymer and from monols for the copolymer. EXAMPLES

Table 1 identifies a list of components from which lubricant formulations are

prepared in each Example (Ex) of the present invention and each Comparative Example

(Comp Ex) which follow.

Function Component Description

Group IV PAO with a typical kinematic viscosity of 8 centiStokes (cSt)

Hydrocarbon Group IV

at 100°C. For Example, SpectraSyn™ 8 PAO Fluid (SpectraSyn is a Base Oil Base Oil

trademark of Exxon Mobil Corporation).

Group ΠΙ mineral oil with a typical kinematic viscosity of 8 centiStokes

Hydrocarbon Group ΠΙ

at 100°C. For example, YUBASE™ 8 brand base oil (YUBASE is a Base Oil Base Oil

trademark of SK Lubricants Co.).

Group Π mineral oil with a typical kinematic viscosity of 6.5 centiStokes

Hydrocarbon Group Π

at 100°C. For example, 225N™ brand base oil (225N is a trademark of Base Oil Base Oil

Phillip 66).

Dodecanol initiated random copolymer of propylene oxide and 1,2- butylene oxide (50/50 weight-ratio) with a typical kinematic viscosity at 40°C of 18 centiStokes, at 100*C of 3.9 centiStokes and average

OSP OSP- 18

molecular weight of 500 grams per mole. For example UCON™ OSP- 18 oil soluble polyalkylene glycol (UCON is a trademark of Union Carbide Corporation).

Butanol initiated random homopolymer of 1,2-butylene oxide with a

SYNALOX

OSP typical kinematic viscosity at 100°C of 9 centiStokes. For example

OA60

SYNALOX™ OA60 oil soluble polyalkylene glycol.

Diol initiated random homopolymer of 1,2-butylene oxide with a typical

SYNALOX

OSP kinematic viscosity at 100°C of 11 centiStokes. For example

OD80

SYNALOX™ OD80 oil soluble polyalkylene glycol.

Sulfurized isobutylene having approximately 45 % sulfur, 40°C viscosity

Sulfurized of 50 centiStokes and 100°C viscosity of 7 centiStokes with a specific

SIB

Olefin gravity of 1.14. For example ELCO 217 sulfurized hydrocarbon from the

Elco Corporation.

Phenol, isopropylated, phosphate, 3: 1 (95%); alcohols, C8-C16 reaction

Anti-wear

310M products with P2O ₅ (<5%); < 5% triphenyl phosphate. For Example, additive

DURAD™ 310M (DURAD is a trademark of Chemtura Corporation).

Sulfur Triazol-derivative commercially available under the tradename K-

NF200

Scavenger CORR™ NF200 (K-CORR is a trademark of King Industries, Inc.)

Sulfur Dimercaptothiodizole derivative commercially available under the

NF410

Scavenger tradename K-CORR™ NF410.

Polydimethylsiloxane (85-100%) with a viscosity of 12,500 centiStokes. Available from DOW CORNING™ Corporation as Dow Corning 200

Antifoamer DC200

Fluid, 12,500 cSt. (DOW CORNING is a trademark of Dow Corning Corporation).

Liquid octylated/butylated diphenylamine. For example, IRGANOX™

Antioxidant L-57

L-57 (IRGANOX is a trademark of BASF SE Company).

Antioxidant L06 Octylated phenyl-alpha-naphthylamine. For example, IRGANOX L06. The synergistic effect of OSP in the lubricant formulations is demonstrated in the following Examples (Exs) and Comparative Examples (Comp Exs) using Group Π, ΠΙ and Group IV hydrocarbon base oils. The same effect is expected for Group I base oils. The different levels of refinement between Groups I, II and ΙΠ hydrocarbon oils are not expected to affect the synergistic effect of the OSP.

All the samples for the present invention are prepared by taking a Group II, ΠΙ and rv base oil and then adding the desired treat rates of OSP. L06 is a solid; and L06 is added to the co-base stock and put on a stir plate at 55 °C for a time until the solid particles dissolve in the solution. Then all the other additives are added to resulting solution at a desired treat rate and the resulting mixture is put on a hot stir plate at 55 °C to homogenize the mixture to form a homogenous formulation.

Comparative Examples A-C: Effect of Increasing Anti-Wear Additive

Table 2 provides gear oil lubricant formulations comprising Group ΙΠ hydrocarbon base oil, sulfurized olefin and a phosphate ester. The formulations contain three different levels of extreme pressure additive. For each formulation the concentration of components are listed in wt% relative to total formulation weight.

Table 2 also contains EP load values and AW performance values for each formulation. Determine EP Load values according the EP performance characterization described above. EP load values are reported both kilogram (kg) and pounds (lb).

Determine AW performance values according to the AW performance characterization described above.

Notably, calculations herein for total sulfur content take into account the fact that SIB is 45 wt% sulfur and NF410 is 36.5 wt% sulfur.

Table 2

Component Comp Ex A Comp Ex B Comp Ex C

Group III Base Oil 93.7 92.2 90.2

SIB 1.5 3.0 5.0

310M anti-wear additive 1.0 1.0 1.0

L-57 antioxidant 1.0 1.0 1.0

L06 antioxidant 1.0 1.0 1.0

DC200 0.002 0.002 0.002

NF200 sulfur scavenger 0.3 0.3 0.3

NF410 sulfur scavenger 1.5 1.5 1.5

Total Sulfur content (wt % of formulation) 1.22 1.9 2.8

Total Phosphorous Content (wt % of formulation) 0.07 0.07 0.07

EP Load value 789 kg/1740 lb 925 kg/2040 lb 998 kg/2200 lb

Anti-wear value (mm) 0.914 0.99 0.996 The data in Table 2 reveals that increasing the extreme pressure additive in the formulation increase the EP load value, but also undesirably increases the anti-wear value and sulfur content of the formulation.

Examples 1-3: Comparative Example A with Oil Soluble Polyalkylene Glycol

Table 3 provides gear oil lubricant formulations based on that for Comparative

Example A, except modified by replacing a portion of the base oil with an OSP. OSP concentrations of 5, 15 and 30 wt% based on total formulation weight are represented by the three Examples.

Table 3 also contains EP load values and AW performance values for each formulation. Determine EP Load values according the EP performance characterization described above. EP load values are reported both kilogram (kg) and pounds (lb).

Determine AW performance values according to the AW performance characterization described above.

Table 3

The data in Table 3 reveals the surprising synergistic effect of including an OSP into a lubricant formulation containing hydrocarbon base oil, sulfurized olefin and phosphate ester. The EP load value and anti-wear additive values are noticeably improved over that of Comparative Example A even though the amounts of EP additive, AW additive, phosphorous and sulfur are the same. The OSP works with the EP additive and AW additive to improve both extreme pressure performance and anti-wear performance without requiring an increase in sulfur or phosphorous concentration.

Comparative Examples D and E: Effect of OSP without Phosphate Ester

Table 4 provides gear oil lubricant formulations based on that for Comparative Example A, except modified by replacing a portion of the base oil with an OSP at a concentration 15 and 30 wt% based on total formulation weight and by removing the phosphate ester AW additive. The intent is to determine if the OSP acts as an AW additive to account for the improvement in AW performance upon addition of the OSP in Examples 1-3.

Table 4 also contains EP load values and AW performance values for each formulation. Determine EP Load values according the EP performance characterization described above. EP load values are reported both kilogram (kg) and pounds (lb).

Determine AW performance values according to the AW performance characterization described above.

Table 4

The results in Table 4 reveal that the OSP is not acting as an AW additive as evidenced by an increase in anti-wear value upon removing the phosphate ester anti-wear additive (compare Comp Ex D to Comp Ex A and Ex 2 and compare Comp Ex E to Comp Ex A and Ex 3). A possible antagonistic effect between EP and AW additives is evident by the increase in EP value between Comp Ex D and Ex 2 and between Comp Ex E and Ex 3. However, the anti-wear value is dramatically increased in the same comparisons.

Hence, the improvement in both EP value and AW value in Exs 1-3 is a result of a synergistic effect between a combination of the sulfurized olefin EP additive, the phosphate ester AW additive and the OSP.

Comparative Examples F-H: Effect of Increasing Anti-Wear Additive

Table 5 provides gear oil lubricant formulations comprising Group IV hydrocarbon base oil, sulfurized olefin and a phosphate ester. The formulations contain three different levels of extreme pressure additive. For each formulation the concentration of components are listed in wt% relative to total formulation weight.

Table 5 also contains EP load values and AW performance values for each formulation. Determine EP Load values according the EP performance characterization described above. EP load values are reported both kilogram (kg) and pounds (lb).

Determine AW performance values according to the AW performance characterization described above.

Table 5

The data in Table 5 reveals that increasing the extreme pressure additive in the formulation increase the EP load value, but also undesirably increases the anti-wear value and sulfur content of the formulation.

Examples 4-6: Comparative Example G with Oil Soluble Polyalkylene Glycol

Table 6 provides gear oil lubricant formulations based on that for Comparative

Example G, except modified by replacing a portion of the base oil with an OSP. OSP concentrations of 5, 15 and 30 wt% based on total formulation weight are represented by the three Examples.

Table 6 also contains EP load values and AW performance values for each formulation. Determine EP Load values according the EP performance characterization described above. EP load values are reported both kilogram (kg) and pounds (lb).

Determine AW performance values according to the AW performance characterization described above.

Table 6

The data in Table 6 reveals the surprising synergistic effect of including an OSP into a lubricant formulation containing hydrocarbon base oil, sulfurized olefin and phosphate ester. The EP load value and anti-wear additive values are noticeably improved over that of Comparative Example G even though the amounts of EP additive, AW additive, phosphorous and sulfur are the same. The OSP works with the EP additive and AW additive to improve both extreme pressure performance and anti-wear performance without requiring an increase in sulfur or phosphorous concentration.

Table 7 describes gear oil lubricant formulations comprising a Group II hydrocarbon base oil, sulfurized olefin and a phosphate ester. The formulations described in Table 7 contain two different levels of extreme pressure additive. For each formulation the concentration of components are listed in wt% relative to total formulation weight.

Table 7 also contains EP load values and AW performance values for each formulation. The EP Load values are determined according the EP performance characterization described above. EP load values are reported both in kilograms (kg) and in pounds (lb). The AW performance values are determined according to the AW performance characterization described above.

The data in Table 7 reveals that by increasing the amount of the extreme pressure additive in the formulation increases the EP load value, but also undesirably increases the anti-wear value and sulfur content of the formulation.

Table 8 describes gear oil lubricant formulations similar to the formulation of Comparative Example I, except that the Comparative Example I formulation is modified by replacing a portion of the base oil with an OSP to provide the formulations of the present invention described in Table 8. Different OSP types with concentration at 15 wt% are represented by the three Examples in Table 8 to demonstrate the effect of different OSP types.

Table 8 also describes EP load values and AW performance values for each formulation. EP Load values are determined according the EP performance characterization described above. EP load values are reported both in kilograms (kg) and in pounds (lb). AW performance values are determined according to the AW performance characterization described above.

Table 8

The data in Table 8 reveals the surprising synergistic effect of including an OSP into a lubricant formulation containing hydrocarbon base oil, sulfurized olefin and phosphate ester. The EP load value and anti-wear additive values are noticeably improved over that of Comparative Example I even though the amounts of EP additive, AW additive, phosphorous and sulfur are the same. The OSP works with the EP additive and AW additive to improve both extreme pressure performance and anti-wear performance without requiring an increase in sulfur or phosphorous concentration.