Ether-Based Lubricant Compositions, Methods and Uses

Abstract

The present invention provides a lubricant composition for an internal combustion engine comprising a base oil of lubricating viscosity, wherein the base oil comprises an ether base stock of formula (A): where: R.sub.a and R.sub.b are aliphatic hydrocarbyl groups and may be the same or different; wherein at least one of R.sub.a and R.sub.b is branched-chain alkyl, alkoxy-substituted-alkyl or cycloalkyl-substituted-alkyl; the lubricant composition further comprising at least one aminic anti-oxidant and/or at least one phenolic anti-oxidant; and wherein the total combined amount of aminic and phenolic anti-oxidant in the lubricant composition is not more than 4.0% by weight of the lubricant composition. In some embodiments, the ether base stock has the formula (1): where: R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are as defined herein. The lubricant composition may be used for lubricating a surface in an internal combustion engine as well as for improving the fuel economy performance and/or piston cleanliness performance of an engine and/or a vehicle, such as an automotive vehicle associated with an internal combustion engine.

##STR00001##

Claims

1. A lubricant composition for an internal combustion engine comprising a base oil of lubricating viscosity, wherein the base oil comprises an ether base stock of formula (A): ##STR00064## where: R.sub.a and R.sub.b are aliphatic hydrocarbyl groups and may be the same or different; wherein at least one of R.sub.a and R.sub.b is branched-chain alkyl, alkoxy-substituted-alkyl or cycloalkyl-substituted-alkyl; the lubricant composition further comprising at least one aminic anti-oxidant and/or at least one phenolic anti-oxidant; and wherein the total combined amount of aminic and phenolic anti-oxidant in the lubricant composition is not more than 4.0% by weight of the lubricant composition.

2. The lubricant composition of claim 1, wherein R.sub.a and R.sub.b are independently selected from alkyl, alkoxy-substituted-alkyl or cycloalkyl-substituted-alkyl, provided that when R.sub.a and R.sub.b are both alkyl, at least one of R.sub.a and R.sub.b is/are branched-chain alkyl.

3. The lubricant composition of claim 1, wherein R.sub.a contains more carbon atoms than R.sub.b.

4. The lubricant composition of claim 1, wherein R.sub.a contains from 12 to 30 carbon atoms, and/or R.sub.b contains from 2 to 20 carbon atoms.

5. The lubricant composition of claim 1, wherein the ether base stock is of formula (1): ##STR00065## where: R.sub.1 and R.sub.2 are alkyl or, together with the carbon atom to which they are attached, cycloalkyl; R.sub.3, R.sub.4 and R.sub.5 are H or alkyl; R.sub.6 is alkyl or ##STR00066## where: R.sub.7 and R.sub.8 are H, alkyl or, together with the carbon atom to which they are attached, cycloalkyl; R.sub.9 is H or alkyl; X is alkylene or is absent; and p is 0, 1, 2 or 3; and m and n are 0, 1, 2 or 3, wherein m is 0 when R.sub.4 and R.sub.5 are H.

6. The lubricant composition of claim 5, wherein R.sub.1 and R.sub.2 are C.sub.1-15 alkyl or, together with the carbon atom to which they are attached, C.sub.5-30 cycloalkyl; and/or wherein R.sub.3, R.sub.4 and R.sub.5 are H or C.sub.1-15 alkyl.

7. The lubricant composition of claim 5, wherein m and n are 0, 1 or 2.

8. The lubricant composition of claim 5, wherein the ether base stock has the formula (4): ##STR00067## where: R.sub.1 and R.sub.4 are alkyl; R.sub.3 and R.sub.5 are H or alkyl.

9. The lubricant composition of claim 5, wherein the ether base stock has the formula (7): ##STR00068## where: R.sub.1 and R.sub.2 are alkyl or, together with the carbon to which they are attached, cycloalkyl; R.sub.3, R.sub.4 and R.sub.5 are H or alkyl; and R.sub.6 is alkyl.

10. The lubricant composition of claim 1, wherein the ether base stock contains a total number of carbons atoms of from 20 to 50.

11. The lubricant composition of claim 1, wherein the ether base stock is prepared from bio-derived feedstock containing greater than 50% by weight of biobased carbon.

12. The lubricant composition of claim 1, wherein the base oil of the lubricant composition comprises greater than 10% by weight of the ether base stock and/or wherein the lubricant composition comprises greater than 50% by weight of the base oil.

13. The lubricant composition of claim 12, wherein the base oil of the lubricant composition further comprises a base stock selected from Group I, Group II, Group III, Group IV and Group V base stocks and mixtures thereof.

14. The lubricant composition of claim 1, wherein the lubricant composition has at least one of: a kinematic viscosity at 40 C. of less than 60 cSt; a kinematic viscosity at 100 C. of less than 12 cSt; a viscosity index of greater than 100; a viscosity at 150 C. and a shear rate of 10.sup.6 s.sup.1 of no greater than 3 cP; and a Noack volatility of less than 25% by weight.

15. The lubricant composition of claim 1, wherein the lubricant composition has at least one of: an oxidative stability performance on a CEC-L-088-02 test indicated by an absolute viscosity increase at 40 C. of no more than 45 cSt; an oxidative stability performance on a CEC-L-109-14 test indicated by an increase in kinematic viscosity at 100 C. of less than 200% at 216 hours and/or less than 200% at 168 hours; a fuel economy performance on a CEC-L-054-96 test of at least 2.5%; and a piston cleanliness performance on a CEC-L-088-02 test indicated by an overall piston merit of at least 8.5.

16. The lubricant composition of claim 1, wherein the total combined amount of aminic and phenolic anti-oxidant in the lubricant composition is not more than 3.0% by weight of the lubricant composition.

17. The lubricant composition of claim 1, wherein the total combined amount of aminic and phenolic anti-oxidant in the lubricant composition is at least 0.25% by weight of the lubricant composition.

18. The lubricant composition of claim 1, wherein the total amount of non-aminic and non-phenolic antioxidant in the lubricant composition is not more than 1.0% by weight of the lubricant composition.

19. The lubricant composition of claim 1, wherein the lubricant composition comprises aminic anti-oxidant or phenolic anti-oxidant but not both aminic anti-oxidant and phenolic anti-oxidant.

20. The lubricant composition of claim 1, wherein the at least one phenolic anti-oxidant is selected from alkylated mono-phenols, alkylated hydroquinones, hydroxylated thiodiphenyl ethers, alkylidenebisphenols, acylaminophenols, and sulphurised alkyl phenols and alkali and alkaline earth metal salts thereof.

21. The lubricant composition of claim 1, wherein the at least one phenolic anti-oxidant is selected from 2-t-butyl-4-heptyl phenol, 2-t-butyl-4-octyl phenol, 2-t-butyl-4-dodecyl phenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-heptylphenol, 2,6-di-t-butyl-4-dodecylphenol, 2-methyl-6-t-butyl-4-heptylphenol, 2-methyl-6-t-butyl-4-dodecylphenol, 4,4-methylenebis(2,6-di-t-butylphenol), 2-bis(4-heptyl-6-t-butylphenol), 2,2-bis(4-octyl-6-t-butylphenol), 2,2-bis(4-dodecyl-6-t-butylphenol), 4, 4-bis(2,6-di-t-butylphenol), 4,4-methylene-bis(2,6-di-t-butylphenol) and derivatives thereof.

22. The lubricant composition of claim 1, wherein the at least one aminic anti-oxidant is selected from alkylated and non-alkylated aromatic amines, alkylated diphenylamines, N-alkylated phenylenediamines, phenyl--naphthylamine, and alkylated phenyl--naphthylamines.

23. The lubricant composition of any claim 1, wherein the at least one aminic anti-oxidant is selected from p,p-dioctylphenylamine, t-octylphenyl--naphthylamine, p-octylphenyl--naphthylamine, monooctyldiphenylamine, N,N-di(2-naphthyl)-p-phenylenediamine, phenyl-1-naphthylamine, phenyl-2-naphthylamine, an alkylphenyl-1-naphthylamine, an alkylphenyl-2-naphthylamine and derivatives thereof.

24. The lubricant composition of claim 1, wherein the amount of phosphorus contained in the lubricant composition is less than 0.5 wt. % based on the total weight of the lubricant composition.

25. The lubricant composition of claim 1, wherein the amount of boron contained in the lubricant composition is from 0.005 wt. % to 0.05 wt. %.

26. The lubricant composition of claim 1, wherein the amount of magnesium contained in the lubricant composition is from 0.025 wt. % to 0.5 wt. %.

27. The lubricant composition of claim 1, wherein the lubricant composition comprises one or more dihydrocarbyl dithiophosphate metal salts in an amount of from 0.01 wt. % to 10.0 wt. %.

28. A method of preparing a lubricant composition, said method comprising providing a base oil as defined in claim 1 and blending the base oil with at least one aminic anti-oxidant and/or at least one phenolic anti-oxidant such that the total combined amount of aminic and phenolic anti-oxidant in the lubricant composition is not more than 4.0% by weight of the lubricant composition, and optionally also blending one or more additional lubricant additives, in order to prepare the lubricant composition.

29. A method of lubricating a surface, said method comprising supplying a lubricant composition as defined in claim 1 to said surface, such as wherein the lubricant composition is supplied to a surface in an internal combustion engine.

30. (canceled)

31. (canceled)

32. A method of improving the fuel economy performance and/or piston cleanliness performance of an engine and/or a vehicle, comprising the step of providing the engine and/or the vehicle with a lubricant composition according to claim 1.

33. (canceled)

Description

[0305] The invention will now be described with reference to the accompanying FIGURE and examples, which are not limiting in nature, in which:

[0306] FIG. 1 is a graph of percentage increase in Kinematic Viscosity at 100 C. against time corresponding to results of CEC-L-109 testing of blended compositions containing Guerbet-derived base stock (GE3) and/or a Group III base stock (Yubase 4) together with varying amounts of aminic oxidant and/or phenolic oxidant as well as other lubricant additives.

EXAMPLES

Example 1Properties of Ether Base Stocks

[0307] Guerbet-derived base stock GE3 of formula (1) was prepared, the structure of which is shown in Table 4.

TABLE-US-00004 TABLE 4 Molecular Chemical Weight Formula Structure GE3 522.97 C.sub.36H.sub.74O [00063]

[0308] The following properties of the base stock were tested:

[0309] Kinematic viscosity at 100 C. (KV100) and kinematic viscosity at 40 C. (KV40) were tested according to ASTM D7279.

[0310] Viscosity index (VI) was calculated according to ASTM D2270.

[0311] Pour point was determined according to ASTM D7346.

[0312] Differential scanning calorimetry (DSC) oxidation onset temperature was tested using a method which was based on ASTM E2009 (method B). According to the method, the base stocks were heated from 50 C. to 300 C., at a rate of 50 C./minute, under a pressure of 500 psi in an aluminium SFI pan. The temperature at which an exotherm was observed was recorded.

[0313] Noack volatility was measured using a method which was based on IP 393 and was considered similar to CEC-L-40-A-93. According to the method, reference oils of known Noack volatility were heated from 40 C. to 550 C. to determine the temperature at which the Noack volatility weight loss of each of the reference oils was reached. The base stocks were subjected to the same process as the reference oils. The Noack weight of the base stocks could be determined based on the results obtained from the reference oils.

[0314] The results of the tests are summarized in Table 5, together with results obtained from a conventional base stock (Yubase 4, a group III base stock).

TABLE-US-00005 TABLE 5 DSC Noack Oxidation volatility KV100 KV40 Pour Point Onset T (% by (cSt) (cSt) VI ( C.) ( C.) weight) GE3 3.9 16.0 143 42 202.89 2.4 Yubase 4 4.2 19.2 126 12 220.00 11.7

[0315] It can be seen that the Guerbet-derived base stock ether has a lower volatility, lower pour point and lower kinematic viscosity as compared to the conventional base oil.

Example 2: Properties of Lubricant Compositions Containing Ether Base Stocks

[0316] Guerbet-derived ether base stock GE3 was blended with conventional base oil additives (additive A, a commercially available additive package providing a dispersant level representative of high performance engine oil between 7 and 10 wt % based on the total weight of the lubricant composition; additive B, a cold-flow improver; additive C, an oxidation inhibitor; and additive D, a viscosity index improver) and conventional base oils (Yubase 4, a group III base oil; and Yubase 6, a group III base oil) to form a lubricant blend. A Baseline blend was also prepared. Yubase 4 was chosen as the main component of the Baseline blend, since it exhibits a similar KV100 to Guerbet-derived ether base stock, GE3. The Baseline blend was believed to be a stringent baseline for comparison, since it is a 5W-30 formulation which meets certain specifications (ACEA A5/B5, API-SN/GF-4). The details of the blended compositions are shown in Table 6 in % by weight

TABLE-US-00006 TABLE 6 Baseline blend GE3 blend Additive A 16.4 16.4 Additive B 0.15 0.15 Additive C 0.1 0.1 Additive D 4 4 Yubase 4 67.45 17.45 Yubase 6 11.9 11.9 GE3 0 50

[0317] No problems with miscibility were encountered during preparation of the blended compositions.

[0318] The blended compositions were tested to see whether the advantageous properties of the base stocks would be reflected in a fully formulated lubricant composition. The following properties were tested:

[0319] Kinematic viscosity at 100 C. (KV100) and kinematic viscosity at 40 C. (KV40) were tested according to ASTM D445 (part of SAE J300).

[0320] Viscosity index (VI) was calculated according to ASTM D2270.

[0321] Cold-cranking simulator (CCS) analysis was carried out at 30 C. according to ASTM D5293 (part of SAE J300).

[0322] High temperature high shear (HTHS) analysis was carried out according to CEC-L-36-A-90.

[0323] Total base number (TBN) was determined according to ASTM D2896.

[0324] Noack volatility was tested according to CEC-L-40-A-93.

[0325] Sulphated ash content was measured according to IP 163.

[0326] The results of the tests are summarized in Table 7.

TABLE-US-00007 TABLE 7 Baseline blend GE3 blend KV40 (cSt) 53.59 44.63 KV100 (cSt) 9.542 8.688 VI 164 177 CCS 30 C. (cP) 4656 2702 HTHS (cP) 2.98 2.75 TBN (mg KOH/g) 11.66 11.44 NOACK (% by weight) 11.2 9.7 Sulphated ash (%) 1.22 1.27

[0327] It can be seen that the properties of the Guerbet-derived base stock are also exhibited in the blended composition. In particular, beneficial viscosity, volatility and cold-flow properties are observed. The Guerbet-derived base stock also exhibited similar HTHS measurements, TBNs and sulphated ash contents to the Baseline blend.

Example 3: CEC-L-85-99 Test

[0328] Blended compositions comprising Guerbet-derived base stock (GE3), a group III base stock (Yubase 4) or a group IV base stock (PAO 4) together with varying amounts of aminic oxidant (a diphenylamine) and/or phenolic oxidant (a substituted phenol) were subjected to the CEC-L-85-99 test, which measures DSC oxidation onset temperature and DSC oxidation induction time of the tested blends. Results obtained from the CEC-L-85-99 testing are shown in Table 8 (compositional data shown in % by weight).

TABLE-US-00008 TABLE 8 Blend A B C D E F G H J K L M Yubase 4 100 99.5 99.5 99 PAO 4 100 99.5 99.5 99 GE3 ether 100 99.5 99.5 99 Aminic AO 0.5 0.5 0.5 0.5 0.5 0.5 Phenolic 0.5 0.5 0.5 0.5 0.5 0.5 AO DSC 221 246 246 254 222 245 249 258 209 236 241 252 oxidation onset temperature ( C.) DSC <3.0 7.5 4.1 20.0 <3.0 10.4 6.0 20.8 <3.0 4.2 3.1 27.8 oxidation induction time (mins)

[0329] The results in Table 8 demonstrate that both the oxidation onset temperature and oxidation induction time is increased, indicating increased oxidative stability, in the ether blends when either phenolic anti-oxidant (Blend K) or aminic anti-oxidant (Blend L) are present (compared against Blend J). Additionally, a substantial increase in oxidation onset temperature and oxidation induction time is observed when both aminic and phenolic anti-oxidants are added (Blend M). Notably, when non-ether blends are compared (Blends B to D and F to H) there is clearly only modest increase in oxidation onset temperature and oxidation induction time when both aminic and phenolic anti-oxidants are present (Blends D and H) compared to when they are present singly (Blends B, C, F and G). This indicates that there are synergistic effects associated with the ether base stock with aminic and phenolic anti-oxidants, which are not observed with the non-ether base stocks. This can be readily seen when comparing the tested blends comprising both aminic and phenolic anti-oxidants present (Blends D, H and M), where moving to the ether based system (Blend M) results in over a 25% increase in oxidation induction time over the group III and IV based systems (Blends D and H).

Example 4: CEC-L-85-99 TestFully Formulated Lubricant Compositions

[0330] Fully formulated lubricant compositions comprising Guerbet-derived base stock (GE3) and a group III base stock (Yubase 4) together with varying amounts of aminic oxidant and/or phenolic oxidant as well as other lubricant additives including (non-borated) dispersant, detergents, viscosity index modifier (VIM) and secondary ZDDP, were subjected to the CEC-L-85-99 test. Results obtained from the CEC-L-85-99 testing are shown in Table 9 (compositional data shown in % by weight).

[0331] The results in Table 9 demonstrate that both the oxidation onset temperature and oxidation induction time is increased, indicating increased oxidative stability, when the level of phenolic anti-oxidant and aminic anti-oxidant is increased in the ether based compositions. Additionally, a substantial increase in oxidation onset temperature and oxidation induction time is observed when both aminic and phenolic anti-oxidants are each added at a level of 0.5 wt. % (Compositions 12 and 16) compared to when one of the aminic or phenolic anti-oxidant is present at a lower concentration of 0.1 wt % (Compositions 10, 11, 14 and 15).

TABLE-US-00009 TABLE 9 Lubricant Composition 1 2 3 4 5 6 7 8 Yubase 4 84.62 84.22 84.22 83.82 84.085 83.685 83.685 83.285 GE3 ether Phenolic AO 0.1 0.5 0.1 0.5 0.1 0.5 0.1 0.5 Aminic AO 0.1 0.1 0.5 0.5 0.1 0.1 0.5 0.5 Detergents 2.18 2.18 2.18 2.18 2.18 2.18 2.18 2.18 Dispersant 6 6 6 6 6 6 6 6 ZDDP 0.535 0.535 0.535 0.535 VM 7 7 7 7 7 7 7 7 DSC 262 261 266 269 267 267 271 266 oxidation onset temperature ( C.) DSC 19.2 29.0 36.1 47.2 43.9 40.0 56.3 45.0 oxidation induction time (mins) Lubricant Composition 9 10 11 12 13 14 15 16 Yubase 4 34.62 34.22 34.22 33.82 34.085 33.685 33.685 33.285 GE3 ether 50 50 50 50 50 50 50 50 Phenolic AO 0.1 0.5 0.1 0.5 0.1 0.5 0.1 0.5 Aminic AO 0.1 0.1 0.5 0.5 0.1 0.1 0.5 0.5 Detergents 2.18 2.18 2.18 2.18 2.18 2.18 2.18 2.18 Dispersant 6 6 6 6 6 6 6 6 ZDDP 0.535 0.535 0.535 0.535 VM 7 7 7 7 7 7 7 7 DSC 258 258 262 266 261 259 269 267 oxidation onset temperature ( C.) DSC 17.2 21.8 30.2 44.6 43.0 41.5 45.2 61.6 oxidation induction time (mins)

[0332] Notably, the presence of ZDDP, in addition to aminic or phenolic anti-oxidants, also surprisingly confers a substantial increase in oxidative stability as shown by the corresponding increases in oxidation onset temperature and oxidation induction time (Compositions 13 to 16 compared to Compositions 9 to 12). Furthermore, this effect is particularly pronounced where aminic and phenolic antioxidants are present in equal amounts of 0.5 wt. % in the ether-based composition (Composition 16). This pronounced effect is not, however, observed in the corresponding non-ether-based system (Composition 8), indicating that there are synergistic effects associated with the combination of an ether base stock together with aminic and phenolic anti-oxidants and ZDDP. The presence of ZDDP therefore offers a further improvement in oxidative stability in the compositions of the invention whilst also contributing to improved anti-wear performance of the lubricant composition.

Example 5: CEC-L-109 Tests

[0333] Fully formulated lubricant compositions comprising Guerbet-derived base stock (GE3) and a group III base stock (Yubase 4) together with varying amounts of aminic oxidant and/or phenolic oxidant, as well as other lubricant additives including (non-borated) dispersant, borated dispersant, detergents, viscosity modifier (VM) and secondary ZDDP, were subjected to the CEC-L-109 test. The CEC-L-109 test is a high temperature oxidation test designed to determine the oxidative stability of an engine lubricant, via the measurement of percentage increase in Kinematic Viscosity at 100 C. (KV 100% change), with lower percentage changes indicative of higher oxidative stability. Results obtained from the CEC-L-109 testing are shown in Table 10 (compositional data shown in % by weight).

TABLE-US-00010 TABLE 10 Lubricant Composition a b c d e f g h i j Yubase 4 84.618 83.818 84.083 83.283 82.484 32.484 82.484 32.484 82.484 32.484 GE3 ether 50 50 50 Phenolic AO 0.1 0.5 0.1 0.5 1 1 1 1 1 1 Aminic AO 0.1 0.5 0.1 0.5 1 1 1 1 1 1 Calcium containing 2.18 2.18 2.18 2.18 2.18 2.18 2.18 2.18 1.32 1.32 detergents Magnesium 0.86 0.86 containing detergent Dispersant 6 6 6 6 6 6 6 6 Borated dispersant 6 6 ZDDP 0.535 0.535 0.334 0.334 0.334 0.334 0.334 0.334 VM 7 7 7 7 7 7 7 7 7 7 Antifoam 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 Average KV100 76.0 64.3 561 too 227 40.7 too 84.4 Too 76.1 change (%) viscous viscous viscous to to to measure measure measure

[0334] The CEC-L-109 test results, in the form of average percentage increase in Kinematic Viscosity at 100 C. from duplicate runs, illustrate the benefit of increasing the total antioxidant concentration (compare the result for Composition b with that of Composition a) as well as the negative impact of the presence of ZDDP on oxidative stability of the non-ether based lubricant compositions in this test (compare results for Compositions a and b with those of Compositions c and d).

[0335] However, it is apparent from the results for Composition f that the oxidative stability of the ether-based compositions as measured by the CEC-L-109 test is not significantly impacted by the presence of ZDDP, where this is clearly not the case for the corresponding non-ether based Composition e, which has the same levels of ZDDP and antioxidants as Composition f (40.7% change for Composition f versus 227% change for Composition e). These results are indicative of synergy between the ether base stock in the lubricant composition and the ZDDP and antioxidant components. This therefore means that greater amounts of ZDDP can be used with the ether compositions of the invention without significantly impacting upon the oxidative stability of the composition, such that the full anti-wear benefit of ZDDP can be realized.

[0336] For lubricant compositions g and h, the presence of 6 wt. % borated dispersant provides approximately 0.021 wt. % of boron (on an elemental basis) to the lubricant compositions. The presence of the borated dispersant and associated boron gives rise to a substantial increase in percentage change in Kinematic Viscosity at 100 C. for the non-ether based Composition g (too viscous to measure). In contrast, the presence of borated dispersant in the ether-based Composition h is well tolerated with only a moderate average percentage increase in Kinematic Viscosity at 100 C. (84.4%). These results demonstrate that oxidative stability of the ether compositions of the invention is substantially maintained despite increases in boron content. This is of particular benefit since an increase in boron in the lubricant composition leads to increased elastomer compatibility and reduced corrosion.

[0337] For lubricant compositions i and j, the presence of 0.86 wt. % magnesium-containing detergent provides approximately 0.072 wt. % magnesium (on an elemental basis) to the lubricant compositions. The presence of the magnesium-containing detergent gives rise to a substantial increase in percentage change in Kinematic Viscosity at 100 C. for the non-ether based Composition i (too viscous to measure). In contrast, the presence of magnesium-containing detergent in the ether-based Composition j is well tolerated with only a moderate average percentage increase in Kinematic Viscosity at 100 C. (76.1%). These results demonstrate that oxidative stability of the ether compositions of the invention is substantially maintained despite increases in magnesium content. This is of particular benefit since an increase in magnesium-containing detergents in the lubricant composition provides reduced sulphated ash level for the same total base number (acid neutralisation capability) compared to calcium-containing detergents.

[0338] The effect of the presence of ZDDP and/or borated dispersant in compositions of the invention (Compositions f and h) compared to conventional non-ether based compositions (Compositions e and g) as discussed above are also illustrated in FIG. 1.

[0339] The results in the above examples demonstrate the benefit of the ether base stocks together with aminic and/or phenolic antioxidants for improving oxidative stability, as well as the additional benefits resulting from a synergy with ZDDP. These results demonstrate that aminic and/or phenolic antioxidants can be used in lower amounts in lubricant compositions comprising ether base stocks in accordance with the invention and achieve similar or better oxidative stability in comparison to conventional non-ether based lubricant compositions. A reduction in aminic anti-oxidant in a lubricant composition for an internal combustion engine has a particular benefit in reducing turbocharger deposits as well as a reduction in copper corrosion and an increase in elastomer compatibility. Meanwhile, a reduction in phenolic antioxidant leads to an improvement in environmental toxicity of the lubricant compositions.

[0340] The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as 40 mm is intended to mean about 40 mm.

[0341] Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

[0342] While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope and spirit of this invention.