text: the present invention is directed in one aspect to lubricant compositions comprising at least one base stock , at least one viscosity enhancer for the base stock , and at least one additive . in general , it is contemplated that these components of the present invention may be present in the compositions in widely varying amounts depending on the particular needs of each application , and all such variations are considered to be within the broad scope of the invention . nevertheless , applicants have found that in certain preferred embodiments , the present lubricant compositions are formulated according to the following preferred ranges of components , it being understood that all percentage values indicated in table 1 are modified by the word “ about ”. with respect to certain preferred embodiments , the base stock comprises at least one low viscosity pao and at least one adipate ester . while it is contemplated that a wide range of relative concentrations of such components may be present , in general it is preferred that the base stock of the present invention comprise in certain embodiments a pao : ester weight ratio of from about 0 . 5 to about 12 : 1 , and more preferably of from about 0 . 5 to about 12 : 1 . in certain embodiments it is also preferred that the viscosity improver comprise a high viscosity pao ( hereinafter hvpao ) and an additional additive selected from the group consisting of pib ( polyisobutylene ), pma ( polymethacrylate ), or ocp ( olefin co - polymer ), and combinations of two or more of these . while it is contemplated that a wide range of relative concentrations of such components may be present , in general it is preferred that the viscosity enhancer of the present invention comprise in certain embodiments an additional additive : hvpao weight ratio of from about 0 to about 4 : 1 , and more preferably of from about 0 . 2 to about 4 : 1 . applicants have found that in certain preferred embodiments the present lubricant compositions are formulated according to the following preferred ranges of components , it being understood that all percentage values indicated in table 2 are modified by the word “ about ”. although it is contemplated that the pao used in connection with the base stock component of the present invention may vary widely in particular properties and / or structures , in certain embodiments the pao component is a pao having a viscosity of from about 4 to about 12 cst . in preferred embodiments the pao is selected from group consisting of paos having a viscosity of about 4 , 6 , 8 , 10 , 12 or combinations of two or more of these . in certain preferred embodiments , the pao used in connection with the base stock component of the present invention is comprised of oligomeric compounds having from 2 to about 3 units , preferably units of 1 - decene . although it is also contemplated that the pao used in connection with the viscosity enhancer component of the present invention may vary widely in particular properties and / or structures , in certain embodiments the pao component of the viscosity enhancer comprises , and preferably in certain embodiments consists essentially of a pao having a viscosity greater than about 40 cst , and even more preferably from about 40 to about 1000 cst . in preferred embodiments , the pao component of the viscosity enhancer is comprised of polymeric compounds having greater than about 50 units , more preferably having greater than about 75 units and even more preferably having greater than about 100 units , preferably units of 1 - decene . applicants believe that , in general , numerous particular compounds or combinations of compounds are available for use in connection with each of the ingredients as described herein . with respect to the optional adipate ester , it is preferred in certain embodiments that the adipate ester comprises a decyl adipate , and even more particularly , of one or more adipate esters selected from the group consisting of di - isodecyl adipate , and di - tridecyl adipate . in a further embodiment , the preferred ester comprises di - isodecyl azelate . in certain preferred embodiments , the present lubricant compositions are formulated in accordance with tables 3 or 4 below , it being understood that the amounts are weight percentages and the each value is understood to be preceded by the word “ about ”. the average horsepower loss (“ ahpl ”) is one measure that can be used to represent the performance of a lubricant composition , particularly an axle or gear oil , with respect to the fuel economy impact on the vehicle in which it will be used . in order to obtain information regarding the relative performance of certain preferred lubricants in accordance with the present invention , a testing protocol is used in which a commercial axle is attached to a dynamometer which measures the input and the output torque on the axle . this test is run for comparison purposes with several commercially available lubricants and also with two formulations in accordance with the preferred embodiments of the present invention . in order to help assess the relative performance of the different lubricant formulations , a commercially available product sold under the trade designation emgard ® 2986 is tested several times ( identified with row headings c1a - c1f ) in order to establish an average value for comparison purposes , which values are reported at the end of table 5 . the results of the test done in connection with the commercially available products are identified across the row headings c1 - c4 in table 5 . the results of the tests performed in connection with four lubricant compositions of the present invention are reported - as e1 - e4 . as can be seen from table 5 , the lubricant composition in accordance with the present invention labeled e2 exhibited a 5 . 4 % relative improvement in energy efficiency compared to the average established for emgard ® 2896 . the formulation designated as e2 in table 5 consisted essentially of ( cas # 770 - 11 - 11 ) di - isodecyl adipate ( 5 %), pao 8 ( 56 . 6 %), pao 100 ( 28 %), angamol ® 6004j ( 10 %), hitec 5739 ( 0 . 3 %), e - 9817u ( 0 . 1 %), with all amounts being reported on the basis of weight percent . also as can be seen from table 5 above , the lubricant composition in accordance with the present invention labeled e3 exhibited a 3 . 7 % relative improvement in energy efficiency compared to the average established for emgard ® 2896 . the formulation designated as e3 in table 5 consisted essentially of ( cas # 770 - 39 - 1 ) diisodecyl adipate ( 5 %), pao 8 ( 56 . 6 %), pao 100 ( 13 %), indopol ® h - 1500 spa ( 13 %), angamol ® 6004j ( 10 %), hitec 5739 ( 0 . 3 %), e - 9817u ( 0 . 1 %), with all amounts being reported on the basis of weight percent . and finally , the lubricant composition in accordance with the present invention labeled e4 exhibited a 4 . 3 % relative improvement in energy efficiency compared to the average established for emgard ® 2896 . the formulation designated as e4 in table 5 consisted essentially of ( cas # 770 - 42 - 1 ) di - isodecyl adipate ( 5 %), pao 8 ( 51 . 6 %), pao 100 ( 33 %), angamol ® 6004j ( 10 %), hitec 5739 ( 0 . 3 %), and e - 9817u ( 0 . 1 %), with all amounts being reported on the basis of weight percent . several properties exist which , at least in certain applications , are considered relevant to the effectiveness of lubricant compositions . tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants . the results of the test done for comparison purposes in connection with the commercially available products are identified under column headings emgard ® 4209 , emgard ® 2986 , comp q and comp s in table 6 . the results of the tests performed in connection with two lubricant compositions of the present invention are based on the same formulation reported in table 5 as e1 and e2 , but labeled in table 6 with row headings cognis # 2 and cognis # 3 , respectively . based upon the results reported in table 6 , it is seen that the lubricant compositions in accordance with the present invention exhibit excellent shear stability and low temperature properties relative to leading commercially available axle lubricants . several properties exist which , at least in certain applications , are considered relevant to the anti - corrosion and anti - wear abilities of lubricant compositions . several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants . the results of the test done for comparison purposes in connection with the commercially available products are identified under column headings emgard ® 4209 , emgard ® 2986 , comp q and comp s in table 7 . the results of the tests performed in connection with two lubricant compositions of the present invention are based on the same formulation reported in table 5 as e1 and e2 , but labeled in table 7 with row headings cognis # 2 and cognis # 3 , respectively . based upon the results reported in table 7 , it is seen that the lubricant compositions in accordance with the present invention exhibit excellent corrosion resistance and wear resistance properties . several properties exist which , at least in certain applications , are considered relevant to the stability of lubricant compositions in the environment of use . several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants . the results of the test done for comparison purposes in connection with the commercially available products are identified under column headings emgard ® 4209 , emgard ® 2986 , comp q and comp s in the table 8 . the results of the tests performed in connection with two lubricant compositions of the present invention are based on the same formulation reported in table 5 as e1 and e2 , but labeled in table 8 with row headings cognis # 2 and cognis # 3 , respectively . based upon the results reported in table 8 , it is seen that the lubricant compositions in accordance with the present invention exhibit excellent stability . several properties exist which , at least in certain applications , are considered relevant to the ability of lubricant compositions to have a positive effect on the control of sludge creation and / or build up in the environment of use . several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants . the results of the test done for comparison purposes in connection with the commercially available products are identified under column headings emgard ® 4209 , emgard ® 2986 , comp q and comp s in the table 9 , and associated fig1 . the results of the tests performed in connection with two lubricant compositions of the present are based on the same formulation reported in table 5 as e1 and e2 , but labeled in table 9 with row headings cognis # 2 and cognis # 3 , respectively . based upon the results reported in table 9 and fig1 , it is seen that the lubricant compositions in accordance with the present invention exhibit excellent sludge control . several properties exist which , at least in certain applications , are considered relevant to the ability of lubricant compositions to resist or reduce the rate of wear of the moving metal parts with which it is in contact in the environment of use . several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants . the results of the test done for comparison purposes in connection with the commercially available products are identified under column headings emgard ® 4209 , emgard ® 2986 , comp q and comp s in the table 10 . the results of the tests performed in connection with two lubricant compositions of the present invention are based on the same formulation reported in table 5 as e1 and e2 , but labeled in table 10 with row headings cognis # 2 and cognis # 3 , respectively . based upon the results reported in table 10 , it is seen that the lubricant compositions in accordance with the present invention exhibit excellent wear resistant properties . the frictional properties of a lubricant composition are in general considered to be highly relevant to the ability of lubricant compositions to exhibit superior performance in the environment of use . several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants . the results of the test done for comparison purposes in connection with the commercially available products are identified under column headings emgard ® 4209 , emgard ® 2986 , comp q and comp s in fig2 . the results of this test in accordance with the present invention are based on the same formulation reported in table 5 as e1 and e2 , but labeled in fig2 as cognis # 2 and cognis # 3 , respectively one method of testing the frictional properties of lubricant is to utilize a 19 . 05 mm ( ¾ inch ) steel ball and 46 mm diameter steel desk . the ball is loaded against the face of the disc and the ball and the disc are driven independently to create a mixed rolling / sliding contact . the force between the ball and disk is measured by a force transducer . additional sensors measure the applied load , the lubricant temperature and ( optionally ) electrical contact resistance between specimens and the relative wear between them . a schematic diagram of such a test apparatus is provided in fig3 . such an apparatus is used to test lubricant compositions in accordance with the present invention , using a film thickness of one to 1000 nm (± 1 nm ), speeds of 0 . 010 - 1 . 0 m / s , loads of 100 n , a slide / roll ratio ( ssr ) of 50 %, contact pressures of up to approximately 3 . 0 gpa , a temperature range of from 40 to 100 ° c ., a power supply of from 100 to about 240 v , a total weight of 50 kg and dimensions ( w × h × d ) of 50 × 50 × 30 cm . the results of this test indicate that lubricant compositions in accordance with preferred aspects of the present invention produce exceptionally low friction coefficients relative to other commercially available lubricant compositions , as identified in fig2 . the traction properties of a fluid in many instances are relevant to the ability of lubricant compositions to exhibit superior performance in the environment of use . several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants . the results of the test done for comparison purposes in connection with the commercially available products are identified under column headings emgard ® 4209 , emgard ® 2986 , comp q and comp s in fig4 . the results of the tests performed in connection with two lubricant compositions of the present invention are based on the same formulation reported in table 5 as e1 and e2 , but labeled in fig4 as cognis # 2 and cognis # 3 , respectively . one method of testing the traction properties of a lubricant composition is to measure the thickness and traction properties of elastohydrodynamic lubricant ( ehl ) films utilizing an apparatus having at least one bowl or roller loaded against the internal diameter of a transparent ring having a larger radius than the bowl or roller . the lubricant to be tested is placed between the rotating roller and arraying thereby forming an ehl film where the ball and arraying contact . roller and arraying rotating speeds are controlled to obtain different amounts of relative sliding motion between the respective surfaces . contact between the surfaces and the resultant film are observed by way of a transparent ring which allows optical measurements of lubricating film thickness . traction forces generated during contact are also measured . a schematic diagram of such a test apparatus is provided in fig5 . such an apparatus is used to test lubricant compositions in accordance with the present invention , using a film thickness of one to 1000 nm (± 1 nm ), speeds of 0 . 010 - 3 . 5 m / s , loads of 1 to 50 n , a slide / roll ratio ( ssr ) of 50 %, contact pressures of up to approximately 3 . 0 gpa , a temperature range of from 40 to 100 ° c ., a power supply of from 100 to about 240 v , a total weight of 50 kg and dimensions ( w × h × d ) of 50 × 50 × 30 cm . the results of this test indicate that lubricant compositions in accordance with preferred aspects of the present invention produced acceptable film thicknesses , especially at temperatures of 40 ° c ., relative to other commercially available lubricant compositions , as identified in fig4 . one property of lubricant compositions which is considered to be important , at least in certain applications , is the compatibility of the lubricant with nonmetal parts in the system and environment of use , especially including seals , gaskets and the like . several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants in connection with seal compatibility . the results of the test done for comparison purposes in connection with the commercially available products are identified under column headings emgard ® 4209 , emgard ® 2986 , comp q and comp s in table 11 and fig6 . the results of the tests performed in connection with two lubricant compositions of the present invention are based on the same formulation reported in table 5 as e1 and e2 , but labeled in table 11 with row headings cognis # 2 and cognis # 3 , respectively . based upon the results reported in table 11 and the associated graph , fig6 , it is seen that the lubricant compositions in accordance with the present invention exhibit , or would be expected to exhibit , excellent compatibility with the seals , gaskets and the like , used in connection with the systems and devices in which the present lubricant compositions are intended to be included .