Abstract:
The present invention is directed to a traction coefficient reducing lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity comprising a blend of two or more isomerized Fischer-Tropsch derived base oils wherein the kinematic viscosity of the blend is in a range from about 2 to about 14 centistokes at 100° C., and (b) one or more lubricating oil additives wherein the lubricating oil composition is essentially free of friction modifiers. The present invention is also directed to a method for reducing the traction coefficient in internal combustion engines comprising lubricating the internal combustion engines with a lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity comprising a blend of two or more isomerized Fischer-Tropsch derived base oils wherein the kinematic viscosity of the blend is in a range from about 2 to about 14 centistokes at 100° C., and (b) one or more lubricating oil additives wherein the lubricating oil composition is essentially free of friction modifiers.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is directed to a traction coefficient reducing lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity comprising a blend of two or more isomerized Fischer-Tropsch derived base oils wherein the kinematic viscosity of the blend is in a range from about 2 to about 14 centistokes at 100° C., and (b) one or more lubricating oil additives wherein the lubricating oil composition is essentially free of friction modifiers. The present invention is also directed to a method for reducing the traction coefficient in internal combustion engines comprising lubricating the internal combustion engines with a lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity comprising a blend of two or more isomerized Fischer-Tropsch derived base oils wherein the kinematic viscosity of the blend is in a range from about 2 to about 14 centistokes at 100° C., and (b) one or more lubricating oil additives wherein the lubricating oil composition is essentially free of friction modifiers. 
       BACKGROUND OF THE INVENTION 
       [0002]    Lubricating oils for internal combustion engines contain one or more additives in addition to at least one base lubricating oil. Lubricating oils are used to perform the critical function of lubricating moving parts in the internal combustion engine. Lubricating oils perform this function by maintaining a sufficiently high lubricating film thickness on metal surfaces in order to maintain low friction and reduce wear of the metal parts. Reduction in friction ultimately results in improved fuel economy and enhanced mechanical efficiency. 
         [0003]    Reduction in friction can be accomplished by reducing the viscosity of the lubricating oil. While this approach works well at higher contact speeds, it may increase wear at lower contact speeds if a sufficiently thick lubricating oil cannot be maintained. Conventional lubricating oils rely on friction reducing agents, such as surface active friction modifiers, for protecting the metal surfaces at these lower contact speeds. 
         [0004]    The present invention describes the use of a new type of base lubricating oil with properties that allow a reduction of friction at high contact speeds without sacrificing the ability to maintain a lubricating oil film at lower contact speeds. Even more surprising was the observation that the lubricating oils of the present invention allowed for a reduction in friction at very low contact speeds without the addition of any surface active friction modifier. 
         [0005]    A number of patents and patent applications have discussed methods for reducing friction by the addition of friction modifiers in lubricating oil compositions. In addition, there are numerous patents and patent applications that disclose Fischer-Tropsch derived base oils that have superior lubricating oil properties. However, none have disclosed a lubricating oil composition comprising a blend of two or more Fischer-Tropsch derived base oils and one or more additives, wherein the lubricating oil composition shows a remarkable reduction in the traction coefficient of the lubricating oil composition such as observed in the present invention, even without the addition of friction modifiers. 
         [0006]    Patent Cooperation Treaty Application No. PCT/US92/10373 (Publication No. WO 93/14049) discloses lubricant compositions comprising blends or mixtures of low viscosity, 3-8 cS, e.g. about 5 cS (100° C.), HVI lube basestock with higher viscosity, 15 cS+ e.g. 30+ cS (100° C.) HVI PAO lube basestock produced from slack wax by thermal cracking to alpha olefins followed by Lewis acid catalyzed oligomerization of the alpha olefin mixture to lube base stock. Blending these components in appropriate proportions produces lube basestock having viscosities in the range of 8-15 cS (100° C.) from which material suitable for formulation of 10 W-30 automobile engine lube can be produced. The blends are notable for exhibiting high VI values greater than that of either component of the blend. 
         [0007]    Patent Cooperation Treaty Application No. PCT/EP02/01352 (Publication NO. WO 02/064711 A1) discloses a lubricant composition comprising a base oil and one or more additions wherein the lubricant compositions has a kinematic viscosity at 100° C. of more than 5.6 cSt, a cold cranking simulated dynamic viscosity at −35° C. according to ASSTM D 5293 of less than 62 centiPoise (cP) and a mini rotary viscosity test value of less than 60,000 cP according to ASTM d 4684, wherein the base oil has been obtained from a waxy paraffinic Fischer-Tropsch synthesized hydrocarbons. 
         [0008]    U.S. patent application Ser. No. 10/320,101 (Publication No. US 2003/0166473 A1) and U.S. patent application Ser. No. 10/320,101 (Publication No. US 2003/0166474 A1) disclose friction reducers for use in lubricating oil compositions which comprise certain groups of aromatic compounds, esters, narrow mixtures of base stocks, and/or amorphous polymers such as amorphous olefin copolymers. These compositions can provide substantial reductions in the coefficient of friction and fuel economy improving benefits when admixed to lubricating oils without deleterious effects such as instability, undesirable high viscosities and deposits. 
         [0009]    UK Patent Application No. 0319242.4 (Publication No. GB 2 392 673 A) discloses a process for preparing Fischer-Tropsch derived lubricating base oils by blending Fischer-Tropsch distillate fraction having a viscosity of 2 or greater but less than 3 cSt at 100° C. with at least one additional Fischer-Tropsch derived distillate fraction having a viscosity of greater than 3.8 cSt at 100° C., lubricating base oil compositions having a viscosity between about 3 and about 10 cSt at 100° C. and a TGA Novack volatility of less than about 35 weight percent; and finished lubricants using aforesaid lubricating base oils. 
         [0010]    U.S. patent application Ser. No. 10/301,391 (Publication No. US 2004/0094453 A1) discloses a process for producing a lubricating base oil blend which comprises (a) recovering a Fischer-Tropsch derived distillate fraction characterized by a kinematic viscosity of 2 or greater but less than 3 cSt at 100° C., and (b) blending the Fischer-Tropsch derived distillate fraction with a petroleum derived base oil selected from the group consisting of a Group I base oil, a Group II base oil, a Group III base oil, and a mixture of two or more of any of the foregoing conventional base oils in the proper proportion to produce a lubricating base oil blend characterized as having a viscosity of about 3 or greater; also the base oil blends, finished lubricants, and their use in internal combustion engines. 
         [0011]    U.S. patent application Ser. No. 10/704,031 (Publication No. US 2005/0098476 A1) discloses a method for improving the lubricating properties of a distillate base oil characterized by a pour point of 0° C. or less and a boiling range having the 10 percent point falling between about 625° F. and about 790° F. and the 90 percent point falling between about 725° F. and about 950° F., the method comprises blending with said distillate base oil a sufficient amount of a pour point depressing base oil blending component to reduce the pour point of the resulting base oil blend at least 3° C. below the pour point of the distillate base oil wherein the pour point depressing base oil blending component is an isomerized Fischer-Tropsch derived bottoms product having a pour point that is at least 3° C. higher than the pour point of the distillate base oil. 
         [0012]    Patent Cooperation Treaty Application NO. PCT/EP04/038849 (Publication No. WO 05/066314 A1) discloses a process for manufacturing a finished lubricant by (a) performing Fischer-Tropsch synthesis on syngas to provide a product stream (b) isolating from said product stream a substantially paraffinic wax feed having less than about 30 ppm total nitrogen and sulfur, and less than about 1 weight percent oxygen (c) dewaxing said feed by hydroisomerization dewaxing using a shape selective intermediate pore size molecular sieve comprising a noble metal hydrogenation component, wherein the hydroisomerization temperature is between about 600° F. (315° C.) and about 750° F. (399° C.), to produce an isomerized oil; and (d) hydrofinishing said isomerized oil, whereby a lubricating base oil is produced having specific desired properties; and (e) blending the lubricating base oil with at least one lubricant additive. 
         [0013]    U.S. patent application Ser. No. 10/835,219 (Publication No. US 2005/0241990 A1) discloses a method of operating a wormgear drive at high efficiency comprising filing an oil reservoir with wormgear lubricant comprising an isomerized Fischer-Tropsch derived distillate fraction having a low traction coefficient and operating the wormgear derive with the filled oil reservoir at an equilibrium temperature between 20 and 225° C. This invention is also directed to a process for reducing the traction coefficient of higher-traction coefficient lubricating base oil by blending it with an isomerized Fischer-Tropsch derived distillate fraction. This invention is also directed to a wormgear lubricant comprising an isomerized Fischer-Tropsch distillate fraction and between 2 and 50 weight percent thickener. 
         [0014]    U.S. patent application Ser. No. 10/949,779 (Publication No. US 2006/0027486 A1) discloses a multigrade engine oil meeting the specifications of SAE J300 revises June 2001 requirements and a process for preparing it, said engine oil comprising (a) between about 15 to about 94.5 weight percent of a hydroisomerized distillate Fischer-Tropsch base oil characterized by (i) a kinematic viscosity between 2.5 and about 8 cSt at 100° C., (ii) at least about 3 weight percent of the molecules having cycloparaffin functionality, and (iii) a ratio of weight percent molecules with monocycloparaffin functionality to weight percent molecules with multiparaffin functionality greater than about 15; (b) between about 0.5 and about 20 weight percent of a pour point depressing base oil blending component prepared from a hydroisomerized bottoms material having an average degree of branching in the molecules between about 5 and about 9 alkyl-branches per 100 carbon atoms and wherein not more than 10 weight percent boils below about 900° 0  F., and (c) between about 5 to about 30 weight percent of an additive package designed to meet the specifications for ILSAC GF-3. 
       SUMMARY OF THE INVENTION 
       [0015]    The present invention is directed to a traction coefficient reducing lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity comprising a blend of two or more isomerized Fischer-Tropsch derived base oils wherein the kinematic viscosity of the blend is in a range from about 2 to about 14 centistokes at 100° C., and (b) one or more lubricating oil additives wherein the lubricating oil composition is essentially free of friction modifiers. The present invention is also directed to a method for reducing the traction coefficient in internal combustion engines comprising lubricating the internal combustion engines with a lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity comprising a blend of two or more isomerized Fischer-Tropsch derived base oils wherein the kinematic viscosity of the blend is in a range from about 2 to about 14 centistokes at 100° C., and (b) one or more lubricating oil additives wherein the lubricating oil composition is essentially free of friction modifiers. 
         [0016]    Specifically, the invention is directed to traction coefficient reducing lubricating oil composition for internal combustion engines comprising:
       (a) a major amount of an oil of lubricating viscosity comprising a blend of two or more isomerized Fischer-Tropsch derived base oils wherein the kinematic viscosity of the blend is in a range from about 2 to about 14 centistokes at 100° C.; and   (b) one or more lubricating oil additives;
 
wherein the lubricating oil composition is essentially free of friction modifiers.
       
 
         [0019]    The traction coefficient reducing lubricating oil composition above further comprises one or more conventional base oils. Preferably the conventional base oil in the lubricating oil composition is a maximum of 30 weight percent based on the total weight percent of the lubricating oil composition. More preferably the conventional base oil in the lubricating oil composition is a maximum of 10 weight percent based on the total weight percent of the lubricating oil composition. 
         [0020]    In a preferred embodiment the of the lubricating oil composition the reduction in the traction coefficient of the lubricating oil composition compared to Group II base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load to 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 25 and at a speed of 10 millimeters per second is in the range of about 17 percent to about 47 percent, at a speed of 100 millimeters per second it is in the range of about 44 percent to about 74 percent and at a speed of 1,000 millimeters per second is in the range of about 25 percent to about 55 percent. Also, preferably the reduction in the traction coefficient of the lubricating oil composition compared to Group II base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 50 and at a speed of 10 millimeters per second is in the range of about 13 percent to about 43 percent, at a speed of 100 millimeters per second it is in the range of about 41 percent to about 71 percent and at a speed of 1,000 millimeters per second is in the range of about 25 percent to about 55 percent. Also, preferably the reduction in the traction coefficient of the lubricating oil composition compared to Group II base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to a roll ratio of 75 and at a speed of 10 millimeters per second is in the range of about 9 percent to about 39 percent, at a speed of 100 millimeters per second it is in the range of about 41 percent to about 71 percent and at a speed of 1,000 millimeters per second is in the range of about 22 percent to about 52 percent. 
         [0021]    In a preferred embodiment the of the lubricating oil composition the reduction in the traction coefficient of the lubricating oil composition compared to Group III base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 25 and at a speed of 10 millimeters per second is in the range of about 3 percent to about 28 percent, at a speed of 100 millimeters per second it is in the range of about 9 percent to about 39 percent and at a speed of 1,000 millimeters per second is in the range of about 10 percent to about 40 percent. Also, preferably the reduction in the traction coefficient of the lubricating oil composition compared to Group III base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 50 and at a speed of 10 millimeters per second is in the range of about 17 percent to about 47 percent, at a speed of 100 millimeters per second it is in the range of about 51 percent to about 81 percent and at a speed of 1,000 millimeters per second is in the range of about 22 percent to about 52 percent. Also, preferably the reduction in the traction coefficient of the lubricating oil composition compared to Group III base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 75 and at a speed of 10 millimeters per second is in the range of about 9 percent to about 39 percent, at a speed of 100 millimeters per second it is in the range of about 44 percent to about 74 percent and at a speed of 1,000 millimeters per second is in the range of about 14 percent to about 44 percent. 
         [0022]    In a preferred embodiment of the lubricating oil composition in (a) the oil of lubricating viscosity blend has a kinematic viscosity in the range from about 3 to about 12 centistokes at 100° C. More preferably the oil of lubricating viscosity blend has a kinematic viscosity in the range from about 4 to about 10 centistokes at 100° C. 
         [0023]    In a further preferred embodiment of the lubricating oil composition the oil of lubricating viscosity is a blend of (i) one or more low kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 2 to about 9 centistokes at 100° C. and (ii) one or more high kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 5 to about 16 centistokes at 100° C. More preferably the oil of lubricating viscosity is a blend of (i) the low kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 3 to about 8 centistokes at 100° C. and (ii) the high kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 6 to about 15 centistokes at 100° C. Most preferably the oil of lubricating viscosity is a blend of (i) the low kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity of about 4 centistokes at 100° C. and (ii) the high kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity of about 14 centistokes at 100° C. 
         [0024]    It is also preferred that the oil of lubricating viscosity blend has isomerized Fischer-Tropsch derived base oils having greater than 95 weight percent saturates. Also preferred is that the oil of lubricating viscosity blend has isomerized Fischer-Tropsch derived base oils having less than 0.3 weight percent aromatics. 
         [0025]    In the oil of lubricating viscosity preferably the (i) in the blend is an isomerized Fischer-Tropsch derived base oil having a ratio of paraffinic carbons to naphthenic carbons in the range of 99.0 weight percent to 1.0 to about 99.4 weight percent to about 0.6 weight percent and (ii) in the blend is an isomerized Fischer-Tropsch derived base oil having a ratio of paraffinic carbons to naphthenic carbons in the range of 97.0 weight percent to 3.0 to about 95.0 weight percent to about 5.0 weight percent. 
         [0026]    Another embodiment of the invention is directed to a traction coefficient reducing lubricating oil compositions for internal combustion engines comprising:
       (a) a major amount of an oil of lubricating viscosity comprising a blend of two or more isomerized Fischer-Tropsch derived base oils wherein the kinematic viscosity of the blend is in a range from about 2 to about 14 centistokes at 100° C.;   (b) one or more detergents;   (c) one or more dispersants;   (d) one or more anti-wear agents; and   (e) one or more anti-oxidants;
 
wherein the lubricating oil composition is essentially free of friction modifiers.
       
 
         [0032]    In a preferred embodiment of the lubricating oil composition (b) is a low, medium or high overbased metal sulfonate, metal phenate, metal salicylate, or any combination thereof; (c) is a post-treated dispersant, a non-post-treated dispersant, or any combination thereof; (d) is a metal di-thio di-phosphate, a metal tri-borate, or any combination thereof; and (e) is a sulfurized molybdenum anti-oxidant, di-phenyl amine, a phenolic anti-oxidant or any combination thereof. 
         [0033]    In a further preferred embodiment of the lubricating oil composition (b) is a mixture of a low overbased alkylaromatic sulfonate, a medium overbased alkylaromatic salicylate and a high overbased alkylphenate; (c) is a mixture of a borated bissuccinimide and an ethylene carbonated bissuccinimide; (d) is a mixture of a zinc di-thiophosphate and a potassium tri-borate; and (e) a mixture of a molybdenium-succinimide complex, an octylbutyl diphenyl amine and a phenolic anti-oxidant. 
         [0034]    In a preferred embodiment the of the above lubricating oil composition the reduction in the traction coefficient of the lubricating oil composition compared to Group II base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 25 and at a speed of 10 millimeters per second is in the range of about 17 percent to about 47 percent, at a speed of 100 millimeters per second it is in the range of about 44 percent to about 74 percent and at a speed of 1,000 millimeters per second is in the range of about 25 percent to about 55 percent. Also, preferably the reduction in the traction coefficient of the lubricating oil composition compared to Group II base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 50 and at a speed of 10 millimeters per second is in the range of about 13 percent to about 43 percent, at a speed of 100 millimeters per second it is in the range of about 41 percent to about 71 percent and at a speed of 1,000 millimeters per second is in the range of about 25 percent to about 55 percent. Also, preferably the reduction in the traction coefficient of the lubricating oil composition compared to Group II base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 MPa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 75 and at a speed of 10 millimeters per second is in the range of about 9 percent to about 39 percent, at a speed of 100 millimeters per second it is in the range of about 41 percent to about 71 percent and at a speed of 1,000 millimeters per second is in the range of about 22 percent to about 52 percent. 
         [0035]    In a preferred embodiment the of the above lubricating oil composition the reduction in the traction coefficient of the lubricating oil composition compared to Group III base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 25 and at a speed of 10 millimeters per second is in the range of about 3 percent to about 28 percent, at a speed of 100 millimeters per second it is in the range of about 9 percent to about 39 percent and at a speed of 1,000 millimeters per second is in the range of about 10 percent to about 40 percent. Also, preferably the reduction in the traction coefficient of the lubricating oil composition compared to Group III base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 50 and at a speed of 10 millimeters per second is in the range of about 17 percent to about 47 percent, at a speed of 100 millimeters per second it is in the range of about 51 percent to about 81 percent and at a speed of 1,000 millimeters per second is in the range of about 22 percent to about 52 percent. Also, preferably the reduction in the traction coefficient of the lubricating oil composition compared to Group III base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 75 and at a speed of 10 millimeters per second is in the range of about 9 percent to about 39 percent, at a speed of 100 millimeters per second it is in the range of about 44 percent to about 74 percent and at a speed of 1,000 millimeters per second is in the range of about 14 percent to about 44 percent. 
         [0036]    The present invention is also directed to a method for reducing the traction coefficient in internal combustion engines comprising lubricating the internal combustion engines with a lubricating oil composition comprising:
       (a) a major amount of an oil of lubricating viscosity comprising a blend of two or more isomerized Fischer-Tropsch derived base oils wherein the kinematic viscosity of the blend is in a range from about 2 to about 14 centistokes at 100; and   (b) one or more lubricating oil additives;
 
wherein the lubricating oil composition is essentially free of friction modifiers.
       
 
         [0039]    The traction coefficient reducing lubricating oil composition for reducing traction coefficient in internal combustion engines further comprises one or more conventional base oils. Preferably the conventional base oil in the lubricating oil composition is a maximum of 30 weight percent based on the total weight percent of the lubricating oil composition. More preferably the conventional base oil in the lubricating oil composition is a maximum of 10 weight percent based on the total weight percent of the lubricating oil composition. 
         [0040]    In the above method, in a preferred embodiment of the lubricating oil composition the reduction in the traction coefficient of the lubricating oil composition compared to Group II base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 25 and at a speed of 10 millimeters per second is in the range of about 17 percent to about 47 percent, at a speed of 100 millimeters per second it is in the range of about 44 percent to about 74 percent and at a speed of 1,000 millimeters per second is in the range of about 25 percent to about 55 percent. Also, preferably the reduction in the traction coefficient of the lubricating oil composition compared to Group II base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 50 and at a speed of 10 millimeters per second is in the range of about 13 percent to about 43 percent, at a speed of 100 millimeters per second it is in the range of about 41 percent to about 71 percent and at a speed of 1,000 millimeters per second is in the range of about 25 percent to about 55 percent. Also, preferably the reduction in the traction coefficient of the lubricating oil composition compared to Group II base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 75 and at a speed of 10 millimeters per second is in the range of about 9 percent to about 39 percent, at a speed of 100 millimeters per second it is in the range of about 41 percent to about 71 percent and at a speed of 1,000 millimeters per second is in the range of about 22 percent to about 52 percent. 
         [0041]    In the above method, in a preferred embodiment the of the lubricating oil composition the reduction in the traction coefficient of the lubricating oil composition compared to Group III base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 25 and at a speed of 10 millimeters per second is in the range of about 3 percent to about 28 percent, at a speed of 100 millimeters per second it is in the range of about 9 percent to about 39 percent and at a speed of 1,000 millimeters per second is in the range of about 10 percent to about 40 percent. Also, preferably the reduction in the traction coefficient of the lubricating oil composition compared to Group III base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 50 and at a speed of 10 millimeters per second is in the range of about 17 percent to about 47 percent, at a speed of 100 millimeters per second it is int eh range of about 51 percent to about 81 percent and at a speed of 1,000 millimeters per second is in the range of about 22 percent to about 52 percent. Also, preferably the reduction in the traction coefficient of the lubricating oil composition compared to Group III base oils at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, a slide to roll ratio of 75 and at a speed of 10 millimeters per second is in the range of about 9 percent to about 39 percent, at a speed of 100 millimeters per second it is in the range of about 44 percent to about 74 percent and at a speed of 1,000 millimeters per second is in the range of about 14 percent to about 44 percent. 
         [0042]    In a preferred embodiment of the method in (a) the oil of lubricating viscosity blend has a kinematic viscosity in the range from about 3 to about 12 centistokes at 100° C. More preferably the oil of lubricating viscosity blend has a kinematic viscosity in the range from about 4 to about 10 centistokes at 100° C. 
         [0043]    In the above method it is preferred that the oil of lubricating viscosity is a blend of (i) one or more low kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 2 to about 9 centistokes at 100° C. and (ii) one or more high kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 5 to about 16 centistokes at 100° C. More preferably the oil of lubricating viscosity is a blend of (i) the low kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 3 to about 8 centistokes at 100° C. and (ii) the high kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 6 to about 15 centistokes at 100° C. Most preferably the oil of lubricating viscosity is a blend of (i) the low kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity of about 4 centistokes at 100° C. and (ii) the high kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity of about 14 centistokes at 100° C. 
         [0044]    It is preferred that in the above method the oil of lubricating viscosity blend has isomerized Fischer-Tropsch derived base oils having greater than 95 weight percent saturates. It is also preferred that the oil of lubricating viscosity blend in the above method have isomerized Fischer-Tropsch derived base oils having less than 0.3 weight percent aromatics. 
         [0045]    In a preferred embodiment of the method the oil of lubricating viscosity is a blend of (i) an isomerized Fischer-Tropsch derived base oil having a ratio of paraffinic carbons to naphthenic carbons in the range of 99.0 weight percent to 1.0 to about 99.4 weight percent to about 0.6 weight percent and (ii) an isomerized Fischer-Tropsch derived base oil having a ratio of paraffinic carbons to naphthenic carbons in the range of 97.0 weight percent to 3.0 to about 95.0 weight percent to about 5.0 weight percent. 
         [0046]    In another embodiment of the above method in the lubricating oil composition (b) is a low, medium or high overbased metal sulfonate, metal phenate, metal salicylate, or any combination thereof; (c) is a treated post-treated dispersant, a non-post-treated dispersant, or any combination thereof; (d) is a metal di-thio di-phosphate or a metal tri-borate, or any combination thereof; and (e) is a sulfurized molybdenum anti-oxidant, di-phenyl amine or a phenolic anti-oxidant, or any combination thereof. 
         [0047]    More preferably (b) in the above embodiment is a mixture of a low overbased alkylaromatic sulfonate, a medium overbased alkylaromatic salicylate and a high overbased alkylphenate; (c) is a mixture of a borated bissuccinimide and a ethylene carbonated bissuccinimide; (d) is a mixture of a zinc di-thiophosphate and a potassium tri-borate; and (e) a mixture of a molybdenum-succinimide complex, an octylbutyl diphenyl amine and phenolic anti-oxidant. 
         [0048]    The present invention is also directed to a traction coefficient reducing lubricating oil concentrate for internal combustion engines comprising:
       (a) comprising from about 10 weight percent to about 90 weight percent of an oil of lubricating viscosity comprising a conventional base oil, or a isomerized Fischer-Tropsch derived base oil, or any combination thereof; and   (b) one or more lubricating oil additives;
 
wherein the lubricating oil concentrate is essentially free of friction modifiers.
       
 
         [0051]    In a preferred embodiment of the above lubricating oil concentrated in (a) the oil of lubricating viscosity has a kinematic viscosity in the range from about 3 to about 12 centistokes at 100° C. More preferably the oil of lubricating viscosity has a kinematic viscosity in the range from about 4 to about 10 centistokes at 100° C. 
         [0052]    In the above lubricating oil concentrate, in (a) in the oil of lubricating viscosity, it is preferred that the Fischer-Tropsch derived base oil is a blend of (i) one or more low kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 2 to about 9 centistokes at 100° C. and (ii) one or more high kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 5 to about 16 centistokes at 100° C. More preferably in the oil of lubricating viscosity the Fischer-Tropsch derived base oil is a blend of (i) the low kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 3 to about 8 centistokes at 100° C. and (ii) the high kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 6 to about 15 centistokes at 100° C. Most preferably in the oil of lubricating viscosity the Fischer-Tropsch derived base oil is a blend of (i) the low kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity of about 4 centistokes at 100° C. and (ii) the high kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity of about 14 centistokes at 100° C. 
         [0053]    In the above embodiment of the lubricating oil concentrate, in the oil of lubricating viscosity in (a) it is preferred that the isomerized Fischer-Tropsch derived base oils having greater than 95 weight percent saturates. In the oil of lubricating viscosity, it is also preferred that the isomerized Fischer-Tropsch derived base oils have less than 0.3 weight percent aromatics. 
         [0054]    In the oil of lubricating viscosity in the lubricating oil concentrate above, also preferred is that the isomerized Fischer-Tropsch derived base oil is a blend of (i) an isomerized Fischer-Tropsch derived base oil having a ratio of paraffinic carbons to naphthenic carbons in the range of 99.0 weight percent to 1.0 to about 99.4 weight percent to about 0.6 weight percent and (ii) an isomerized Fischer-Tropsch derived base oil having a ratio of paraffinic carbons to naphthenic carbons in the range of 97.0 weight percent to 3.0 to about 95.0 weight percent to about 5.0 weight percent. 
         [0055]    A further embodiment of the present invention is a traction coefficient reducing lubricating oil concentrate for internal combustion engines comprising:
       (a) a major amount of an oil of lubricating viscosity comprising a conventional base oil, or an isomerized Fischer-Tropsch derived base oil, or any combination thereof;   (b) one or more detergents;   (c) one or more dispersants;   (d) one or more anti-wear agents; and   (e) one or more anti-oxidants;
 
wherein the lubricating oil concentrate is essentially free of friction modifiers.
       
 
         [0061]    In the above lubricating oil concentrate, in (a) in the oil of lubricating viscosity, it is preferred that the Fischer-Tropsch derived base oil is a blend of (i) one or more low kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 2 to about 9 centistokes at 100° C. and (ii) one or more high kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 5 to about 16 centistokes at 100° C. More preferably in the oil of lubricating viscosity the Fischer-Tropsch derived base oil is a blend of (i) the low kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 3 to about 8 centistokes at 100° C. and (ii) the high kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity ranging from about 6 to about 15 centistokes at 100° C. Most preferably in the oil of lubricating viscosity the Fischer-Tropsch derived base oil is a blend of (i) the low kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity of about 4 centistokes at 100° C. and (ii) the high kinematic viscosity isomerized Fischer-Tropsch derived base oil having a kinematic viscosity of about 14 centistokes at 100° C. 
         [0062]    In the above embodiment of the lubricating oil concentrate, in the oil of lubricating viscosity in (a) it is preferred that the isomerized Fischer-Tropsch derived base oils having greater than 95 weight percent saturates. In the oil of lubricating viscosity, it is also preferred that the isomerized Fischer-Tropsch derived base oils have less than 0.3 weight percent aromatics. 
         [0063]    In the oil of lubricating viscosity in the lubricating oil concentrate above, also preferred is that the isomerized Fischer-Tropsch derived base oil is a blend of (i) an isomerized Fischer-Tropsch derived base oil having a ratio of paraffinic carbons to naphthenic carbons in the range of 99.0 weight percent to 1.0 to about 99.4 weight percent to about 0.6 weight percent and (ii) an isomerized Fischer-Tropsch derived base oil having a ratio of paraffinic carbons to naphthenic carbons in the range of 97.0 weight percent to 3.0 to about 95.0 weight percent to about 5.0 weight percent. 
         [0064]    Friction modifiers that are not employable in the lubricating oil composition of the present invention are, generally compounds that have C 10 -C 20  hydrocarbyl chains with a polar head. These include ash-containing as well as ashless friction modifiers. Friction modifiers that are excluded from the lubricating oil composition, include, but are not limited to, fatty alcohols, fatty acids, such as stearic acid, isostearic acid, oleic acid and other fatty acids or salts and esters thereof, borated esthers, amines, phosphates, and di- and tri-hydrocarbyl phosphates, hydrocarbyl phosphites and phosphonates. Friction modifiers may also contain molybdenum. Also excluded are organic polymer friction modifiers, for example methacrylates. 
         [0065]    The lubricating oil compositions described above may also contain viscosity index improvers such as olefin copolymers, examples of which are ethylene-propylene copolymers, styrene-isoprene copolymers, hydrated styrene-isoprene copolymers, polybutene, polyisobutylene and vinylpyrrolidone and dispersant type viscosity index improvers. 
         [0066]    Pour point depressants that lower the temperature at which the fluid will flow or can be poured may also be included in the lubricating oil composition of the present invention. Additives that optimize the low temperature fluidity of the lubricating oil are various copolymers. Preferred are pour point depressants that do not have friction modifying properties. 
         [0067]    The addition of rust inhibitors to the lubricating oil composition of the present invention is also contemplated. Preferred Rust inhibitors include nonionic polyoxyethylene surface active agents, such as polyoxyethylene lauryl ether, polyoxyethylene higher alcohol ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene octyl stearyl ether polyoxyethylene oleyl ether, polyoxyethylene sorbitol monostearate, polyoxyethylene sorbitol mono-oleate, and polyethylene glycol mono-oleate. Other compounds that may also be employed as rust inhibitors include stearic acid and other fatty acids, di-caroxylic acids, metal soaps, fatty acid amine salts, metal salts of heavy sulfonic acid, partial carboxylic acid ester of polyhydric alcohol, and phosphoric ester, However, the more preferred rust inhibitors are those that do not contribute to the phosphorous or sulfur content of the lubricating oil. Some of the above listed rust inhibitors may have friction modifying properties. However, these could be added in quantities sufficient for rust inhibition, but not high enough to provide their friction modifying property. 
         [0068]    Extreme pressure agents that may be used in the lubricating oil composition of the present invention include alkaline earth metal borated extreme pressure agents and alkali metal borated extreme pressure agents. Extreme pressure agents containing molybdenum may also be employed in the lubricating oil composition of the present invention. Sulfurized olefins, zinc dialkyl-1-dithiophosphate (primary alkyl, secondary alkyl, and aryl type), di-phenyl sulfide, methyl tri-chlorostearate, chlorinated naphthalene, fluoroalkylpolysiloxane, lead naphthenate, neutralized or partially neutralized phosphates, di-thiophosphates, and sulfur-free phosphates. 
         [0069]    Preferred corrosion inhibitors that may be employed in the lubricating oil of the present invention are derivatives of di-phenyl amines, derivatives of succinimides, sulfurized olefins and the co-sulfurized alkenyl ester/alpha olefin corrosion inhibitors. The corrosion inhibitors also include metal di-thiophosphates, especially zinc di-alkyl di-thiophosphate. More preferred corrosion inhibitors are the derivatives of succinimides. Most preferred are terephthalic acid succinimide complexes. 
         [0070]    Metal deactivators that are employable in the lubricating oil of the present invention include di-salicylidene propylenediamine, triazole derivatives, mercaptobenzothiazoles, thiodiazole derivatives, and mercaptobenzimidazoles. 
         [0071]    Useful foam inhibitors for the present invention are silcon-based. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0072]      FIG. 1  is a comparison of measured points on the Stribeck curves and shows differences for the Group II, Group III and the lubricating oil composition containing Fischer-Tropsch derived base oils. 
           [0073]      FIGS. 2 ,  3  and  4  show the traction coefficient measured at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, for three different contact speeds and slide to roll ratio (SRR) of 25, 50 and 75 respectively for the Group II, Group III and the lubricating oil composition containing Fischer-Tropsch derived base oils. The SRR for lubricating oil composition containing Fischer-Tropsch derived base oils is consistently lower than the observed for the Group II and Group III samples. 
           [0074]      FIG. 5  shows the traction coefficient as a function of average contact speed for the point where the traction coefficient reaches its minimum. The data show that the use of Fischer-Tropsch derived base oils in the lubricating oil composition allows for a reduction in the traction coefficient as well as a reduction in the speed where the contact transitions from hydrodynamic to boundary lubrication. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Definitions 
       [0075]    As used herein, the following terms have the following meanings unless expressly stated to the contrary: 
         [0076]    The term “conventional base oil” as used herein refers to base oil or lubricating oil which may be mineral oil for synthetic oils of lubricating viscosity derived from natural or synthetic sources. Mineral oil for use as the base oil in this invention includes paraffinic, naphthenic and other oils that are ordinarily used in lubricating oil compositions. Synthetic oils include hydrocarbon synthetic oils and synthetic ester. Useful synthetic hydrocarbon oils include liquid polymers and alpha-olefins having the proper viscosity. Base oils include those that are preferably useful in the crankcase of an internal combustion engine. Crankcase lubricating oils ordinarily have a viscosity of about 1300 centistokes at −17.8° C. to 22.7 centistokes at 98.9° C. Below are listed the American Petroleum Institute&#39;s base oil categories Group I-V. Preferred are base oils in Groups I-V. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
             
           
               
                   
               
               
                 API Base Oil Categories 
               
             
          
           
               
                   
                 Base Oil 
                   
                   
                 Saturates 
                 Viscosity 
               
               
                   
                 Category 
                 Sulfur (%) 
                   
                 (%) 
                 Index 
               
               
                   
                   
               
               
                   
                 Group I 
                 &gt;0.03 
                 and/or 
                 &lt;90 
                 80 to 120 
               
               
                   
                 Group II 
                 &lt;0.03 
                 and 
                 &gt;90 
                 80 to 120 
               
               
                   
                 Group III 
                 &lt;0.03 
                 and 
                 &gt;90 
                 &gt;120 
               
             
          
           
               
                   
                 Group IV 
                 PAO synthetic lubricants 
               
               
                   
                 Group V 
                 All other base oils not included in Group I, II, III, IV 
               
               
                   
                   
               
             
          
         
       
     
         [0077]    The term “essentially free” as used herein refers to the friction modifier content in the lubricating oil composition of the present invention. Preferably friction modifier content in the lubricating oil composition is less than 0.2 weight percent based on the total weight of the lubricating oil composition. More preferably the friction modifier content in the lubricating oil composition is less than 0.1 weight percent based on the total weight of the lubricating oil composition. Even more preferably the friction modifier content in the lubricating oil composition is less than 0.05 weight percent based on the total weight of the lubricating oil composition. Most preferably the friction modifier content in the lubricating oil composition is 0.0 weight percent based on the total weight of the lubricating oil composition. 
         [0078]    The term “traction coefficient” as used herein refers to the force that needs to be applied to overcome the resistance between two contacting surfaces in relation to surface pressure in that contact. The traction coefficient measurement was conducted at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, slide to roll ratios of 25, 50 and 75 at a speed of 10, 100 and 1,000 millimeters per second. 
         [0079]    The term “low, medium and high overbased” as used herein refers to alkali metal and alkaline earth metal content of the detergents. Low overbased refers to alkali metal or alkaline earth metal detergents having a Total Base Number (TBN) greater than 1 and less than 20, medium overbased refers to alkali metal or alkaline earth metal detergents having a TBN greater than 20 and less than 200. High overbased refers to alkali metal or alkaline earth metal detergents having a TBN greater than 200. 
         [0080]    The terms “slide or roll ratio or SRR” as used herein refer to the number representing the speed difference as a percentage of the average speed of the two surfaces where both the disk speed and the ball speed are controlled individually. For any of the SRR values applied in the measurements, both surfaces are moving in the same direction, but not at the same speed, thus creating a mixture of a sliding and a rolling motion. 
         [0081]    Unless otherwise specified, all percentages are in weight percent. 
       Lubricating Oil Composition 
       [0082]    It has been discovered that the use of Fischer-Tropsch derived base oils in lubricating oil compositions for international combustion engines allow for a reduction in the traction coefficient as well as a reduction in the speed at which the contact transitions from hydrodynamic to boundary lubrication. This result was unexpected because the reduction in the traction coefficient is observed at high speed as well as at low speed. 
         [0083]    At the highest speed of 1000 millimeters per second, the contact is operating in the hydrodynamic lubrication regime. A reduction in the traction coefficient suggests a reduction in the frictional loss due to shearing in the lubricant film. Such a reduction would mostly impact the traction coefficient at higher contact speed, and would tend to increase the speed where the minimum traction coefficient is observed. 
         [0084]    In addition to seeing a reduction in the traction coefficient at higher contact speeds, unexpectedly, significant reduction in the traction coefficient were also observed at contact speeds of 100 millimeters per second and 10 millimeters per second. Given the higher traction coefficients at these speeds, it is concluded that the contact is operating in a mixed or boundary lubrication regime, where the frictional loss in the lubricant film itself is a negligible part of the traction coefficient. A reduction of the traction coefficient at low speeds suggest that Fischer-Tropsch derived base oil allows for reduced frictional loss due to metal-to-metal contact. Such a reduction in the traction coefficient at low speed would tend to decrease the speed where the minimum traction is observed. 
         [0085]    Furthermore, the traction coefficient observed for the lubricating oil composition containing Fischer-Tropsch derived base oils is lower than the traction coefficient observed for lubricating oil compositions containing Group II or Group III base oils. The comparative reduction observed in the traction coefficient is summarized in Table I below. 
         [0000]    
       
         
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE I 
               
             
             
               
                   
                   
               
               
                   
                 Speed 
               
               
                   
                 (millimeters per second) 
               
             
          
           
               
                   
                 10 
                 100 
                 1,000 
               
               
                   
                   
               
             
          
           
               
                   
                 SSR 25 
                   
                   
                   
               
               
                   
                 Group II Base Oil 
                 17 to 47 
                 44 to 74 
                 25 to 55 
               
               
                   
                 Group III Base Oil 
                  3 to 28 
                  9 to 39 
                 10 to 40 
               
               
                   
                 SSR 50 
               
               
                   
                 Group II Base Oil 
                 13 to 43 
                 41 to 71 
                 25 to 55 
               
               
                   
                 Group III Base Oil 
                 17 to 47 
                 51 to 81 
                 22 to 52 
               
               
                   
                 SSR 75 
               
               
                   
                 Group II Base Oil 
                  9 to 39 
                 41 to 71 
                 22 to 52 
               
               
                   
                 Group III Base Oil 
                  9 to 39 
                 44 to 74 
                 14 to 44 
               
               
                   
                   
               
             
          
         
       
     
         [0086]    The lubricating oil composition of the present invention may be prepared by simple blending or mixing of the compounds described in more detail below. These compounds may also be preblended as a concentrate or package with various other additives in appropriate ratios to facilitate blending of a lubricating oil composition containing the desired concentration of additives. 
       Oil of Lubricating Viscosity 
       [0087]    Oil of lubricating viscosity, or base oil as used herein refer to lubricating oils which may be mineral oil and synthetic oils of lubricating viscosity and preferably useful in the crankcase of an internal combustion engine. Crankcase lubricating oils ordinarily have a viscosity of about 1300 centistokes at −17.8° C. to 22.7 centistokes at 98.9° C. 
         [0088]    The lubricating oils may be derived from synthetic or natural sources. Mineral oil for use as the base oil in this invention includes paraffinic, naphthenic and other oils that are ordinarily used in lubricating oil compositions. Most preferred are Fischer-Tropsch derived base oils. These are prepared as described below. 
       Fischer-Tropsch Synthesis 
       [0089]    In Fischer Tropsch chemistry, syngas is converted to liquid hydrocarbons by contact with a Fischer Tropsch catalyst under reactive conditions. Typically, methane and optionally heavier hydrocarbons (ethane and heavier) can be sent through a conventional syngas generator to provide synthesis gas. Generally, synthesis gas contains hydrogen and carbon monoxide, and may include minor amounts of carbon dioxide and/or water. The presence of sulfur, nitrogen, halogen, selenium, phosphorus and arsenic contaminants in the syngas is undesirable. For this reason and depending on the quality of the syngas, it is preferred to remove sulfur and other contaminants from the feed before performing the Fischer-Tropsch chemistry. Means for removing these contaminants are well known to those of skill in the art. 
         [0090]    In the Fischer-Tropsch process, contacting a synthesis gas comprising a mixture of H 2  and CO with a Fischer-Tropsch catalyst under suitable temperature and pressure reactive conditions forms liquid and gaseous hydrocarbons. Examples of conditions for performing Fischer-Tropsch type reactions are well known to those of skill in the art. 
         [0091]    The fractions of the Fischer-Tropsch synthesis process may range from C 1  to C 200+  with a majority in the C 5  to C 100+  range. The reaction can be conducted in a variety of reactor types, such as fixed bed reactors containing one or more catalyst beds, slurry reactors, fluidized bed reactors, or a combination of different type reactors. Such reaction processes and reactors are well known and documented in the literature. 
         [0092]    The slurry Fischer-Tropsch process, which is preferred in the practice of the invention, utilizes superior heat (and mass) transfer characteristics for the strongly exothermic synthesis reaction and is able to produce relatively high molecular weight, paraffinic hydrocarbons when using a cobalt catalyst. A particularly preferred Fischer-Tropsch process is taught in European Patent Application No. 9400600.7 (Publication No. EP 060 9079 B1). 
         [0093]    In general, Fischer Tropsch catalysts contain a Group VII transition metal on a metal oxide support. The catalysts may also contain a noble metal promoter(s) and/or crystalline molecular sieves. Suitable Fischer-Tropsch catalysts comprise one or more of Fe, Ni, Co, Ru and Re, with cobalt being preferred. A preferred Fischer-Tropsch catalyst comprises effective amounts of cobalt and one or more of Re, Ru, Pt, Fe, Ni, Th, Zr, Hf, U, Mg and La on a suitable inorganic support material, preferably one which comprises one or more refractory metal oxides. Useful catalysts and their preparation are known and illustrated in U.S. Pat. No. 4,568,663, which is intended to be illustrative but not limiting the selection of the catalyst. 
         [0094]    A particularly preferred Fischer-Tropsch process is taught in European Patent Application No. 9400600.7 (Publication No. EP 060 9079 B1). Examples of processes producing waxes of higher carbon number distribution are taught in PCT International Application PCT/98EP/08545 (Publication No. WO9934917 A1). 
         [0095]    The fractions from Fischer-Tropsch reactions generally include a light reaction fraction and a waxy reaction fraction, which typically contain predominantly paraffins. It is the waxy reaction fraction (i.e., the wax fraction) that is used as a feedstock to the process for providing the Fischer-Tropsch derived lubricating base oil used in the blended lubricants and blended finished lubricants of the present invention. 
         [0096]    The isomerized Fischer-Tropsch distillate fractions with low traction coefficients are prepared from the waxy fractions of the Fischer-Tropsch syncrude by a process including hydroisomerization. Preferably, the Fischer-Tropsch lubricant base oils are made by a process as described in U.S. Pat. No. 7,083,713, and U.S. patent application Ser. No. 10/744,870, filed Dec. 23, 2003, and herein incorporated by reference in their entirety. 
       Hydroisomerization 
       [0097]    Hydroisomerization is intended to improve the cold flow properties of the lubricating base oil by the selective addition of branching into the molecular structure. Hydoisomerization ideally will achieve high conversion levels of the Fischer-Tropsch wax to non-waxy iso-paraffins while at the same time minimizing the conversion by cracking. 
         [0098]    Hydroisomerization catalysts useful in the present invention comprise a shape selective intermediate pore size molecular sieve and optionally a catalytically active metal hydrogenation component on a refactory oxide support. Preferred shape selective intermediate pore size molecular sieves used for hydroisomerization are based upon aluminum phosphates, with SAPO-11 being preferred. SM-3 is a particularly preferred shape selective intermediate pore size SAPO, which has a crystalline structure falling within that of the SAPO-11 molecular sieves. The preparation of SM-3 and its unique characteristics are described in U.S. Pat. Nos. 4,943,424 and 5,158,665. Other shape selective intermediate pore size molecular sieves used for hydroisomerization are zeolites, and SSZ-32 and ZSM-23 are preferred. 
         [0099]    A particularly preferred intermediate pore size molecular sieve, which is useful in the present process, is described in U.S. Pat. Nos. 5,135,638 and 5,282,958, the contents of which are hereby incorporated by reference in their entirety. 
         [0100]    Hydroisomerization catalysts useful in the present invention comprise a catalytically active hydrogenation metal. The presence of a catalytically active hydrogenation metal leads to fraction improvement, especially VI and stability. Typically catalytically active hydrogenation metals include chromium, molybdenum, nickel, vanadium, cobalt, tungsten, zinc, platinum, and palladium. The metals platinum and palladium are especially preferred, with platinum most especially preferred. 
         [0101]    The refractory oxide support may be selected from those oxide supports, which are conventionally used for catalysts, including silica, alumina, silica-alumina, magnesia, titania and combinations thereof. 
         [0102]    Suitable conditions for performing hydroisomerization are described in U.S. Pat. Nos. 5,282,958 and 5,135,638, the contents of which are incorporated by reference in their entirety. 
         [0103]    Hydrogen is present in the reaction zone during the hydroisomerization process. Hydrogen may be separated from the fraction and recycled to the reaction zone. 
       Hydrotreating 
       [0104]    Waxy feed to the hydroisomerization process may be hydrotreated prior to hydroisomerization dewaxing. Hydrotreating refers to a catalytic process, usually carried out in the presence of free hydrogen, in which the primary purpose is the removal of various metal contaminants, such as arsenic, aluminum, and cobalt; heteroatoms, such as sulfur and nitrogen; oxygenates; or aromatics from the feed stock. 
         [0105]    Catalysts used in carrying out hydrotreating operations are well known in the art, for example, U.S. Pat. Nos. 4,347,121 and 4,810,357, the contents of which are hereby incorporated by reference in their entirety. Other suitable catalysts are described, for example, in U.S. Pat. Nos. 4,157,294 and 3,904,513. The non-noble hydrogenation metals, such as nickel-molybdenum, are usually present in the final catalyst composition as oxides. 
         [0106]    Typical hydrotreating conditions vary over a wide range. 
       Hydrofinishing 
       [0107]    Hydrofinishing is a hydrotreating process that may be used as a step following hydroisomerization to provide the Fischer-Tropsch lubricating base oil. Hydrofinishing is intended to improve oxidation stability. UV stability, and appearance of the Fischer-Tropsch lubricating base oil fraction by removing traces of aromatics, olefins, color bodies, and solvents. A general description of hydrofinishing may be found in U.S. Pat. Nos. 3,852,207 and 4,673,487. 
         [0108]    The conditions for hydrofinishing will be tailored to achieve an isomerized Fischer-Tropsch derived distillate fraction comprising weight percent aromatics less than 0.30. 
         [0109]    Suitable hydrofinishing catalysts include noble metals from Group VIIIA, such as platinum or palladium or an alumina or silceous matrix, and unsulfided Group VIIIA and Group VIB, such as nickel-molybdenum or nickel-tin on an alumina or silica matrix. U.S. Pat. No. 3,852,207 describes a suitable noble metal catalyst and mild conditions. Other suitable catalysts are described in U.S. Pat. Nos. 4,157,294 and 3,904,513. 
         [0110]    Clay treating to remove impurities is an alternative final process step to provide an isomerized Fischer-Tropsch derived distillate fraction having a low traction coefficient. 
       Fractionation 
       [0111]    The separation of Fischer-Tropsch derived fractions and petroleum derived fractions into various fractions having characteristic boiling ranges in generally accomplished by either atmospheric or vacuum distillation or by a combination of atmospheric and vacuum distillation. Fractionating the lubricating base oil into different boiling range cuts enables the lubricating base oil manufacturing plant to produce more than one grade, or viscosity, or lubricating base oil. 
         [0112]    The isomerized Fischer-Tropsch derived distillate fractions of this invention make excellent lubricating base oils. The isomerized Fischer-Tropsch derived distillate fractions used in carrying out the invention are characterized by having a low traction coefficient, a weight percent aromatics less than 0.30 and extremely low levels of unsaturates. 
       Solvent Dewaxing 
       [0113]    The process to make an isomerized Fischer-Tropsch derived distillate fraction having a low traction coefficient may also include a solvent dewaxing step following the hydroisomerization process. Solvent dewaxing optionally may be used to remove small amounts of remaining waxy molecules from the lubricating base oil after hydroisomerization dewaxing. Solvent dewaxing is done by dissolving the lubricating base oil in a solvent, such as methyl ethyl ketone, methyl iso-butyl ketone, or toluene, and precipitating the wax molecules. Solvent dewaxing is described in U.S. Pat. Nos. 4,477,333, 3,773,650 and 3,775,288 and 7,018,525. 
         [0114]    Conventional synthetic oils include hydrocarbon synthetic oils and synthetic esters. Useful synthetic hydrocarbon oils include liquid polymers of alpha-olefins having the proper viscosity. Especially useful are the hydrogenated liquid oligomers of C 6  to C 12  alpha-olefins such as 1-decene trimer. Similarly, alkyl benzenes of proper viscosity, such as didodecyl benezene, may be used. Useful synthetic esters include the esters of mono-carboxylic acids and polycarboxylic acids as well as mono-hydroxy alkanols and polyols. Typical examples are didodecyl adipate, pentaerthritol tetracapoate, di-2-ethylhexyl adipate, di-laurylsebacate and the like. Complex esters prepared from mixtures of mono- and di-carboxylic acid and mono- and di-hydroxy alkanols can also be used. 
         [0115]    Blends of hydrocarbon oils and synthetic oils may also be used. For example, blends of 10 weight percent to 25 weight percent hydrogenated 1-decene trimer with 75 weight percent to 90 weight percent 683 centistokes at 37.8° C. mineral oil gives an excellent oil base 
         [0116]    Below are listed the American Petroleum Institute&#39;s (API) base oil categories, Group I-V. Preferred are base oils in Groups II-V. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
             
           
               
                   
               
               
                 API Base Oil Categories 
               
             
          
           
               
                   
                 Base Oil 
                   
                   
                 Saturates 
                 Viscosity 
               
               
                   
                 Category 
                 Sulfur (%) 
                   
                 (%) 
                 Index 
               
               
                   
                   
               
               
                   
                 Group I 
                 &gt;0.03 
                 and/or 
                 &lt;90 
                 80 to 120 
               
               
                   
                 Group II 
                 &lt;0.03 
                 and 
                 &gt;90 
                 80 to 120 
               
               
                   
                 Group III 
                 &lt;0.03 
                 and 
                 &gt;90 
                 &gt;120 
               
             
          
           
               
                   
                 Group IV 
                 PAO synthetic lubricants 
               
               
                   
                 Group V 
                 All other base oils not included in Group I, II, III, IV 
               
               
                   
                   
               
             
          
         
       
     
       Dispersants 
       [0117]    The lubricating oil composition of the present invention contains dispersants. Typically, the ashless dispersants are nitrogen-containing dispersants formed by reacting alkenyl succinic acid anhydride with an amine. Examples of such dispersants are alkenyl succinimides and succinamides. These dispersants can be further modified by reaction with, for example, boron or ethylene carbonate. Ester-based ashless dispersants derived from long chain hydrocarbon-substituted carboxylic acids and hydroxy compounds may also be employed. Preferred ashless dispersants are those derived from polyisobutenyl succinic anhydride. A large number of dispersants are commercially available. 
       Anti-Wear Agents 
       [0118]    Traditional wear inhibitors may be employed in the lubricating oil compositions of this invention. As their name implies, these agents reduce wear of moving metallic parts. Examples of such anti-wear agents include, but are not limited to phosphates, phosphites, carbamates, esters, sulfur containing compounds, and molybdenum complexes. The lubricating oil composition of this invention may comprise one or more anti-wear agents, such as metal di-thio di-phosphates and metal di-thiocarbamates or mixtures thereof. A preferred anti-wear agent for use in this invention comprises zinc di-thio di-phosphate. 
       Anti-Oxidants 
       [0119]    Anti-oxidants are used in lubricating oils for inhibition of decomposition processes that occur naturally in lubricating oils as they age or oxidize in the presence of air. These oxidation processes may cause formation of gums, lacquers and sludge resulting in an increase in acidity and viscosity. Examples of useful anti-oxidants are hindered phenol oxidation inhibitors, such as 4,4′-methylene-bis(2,6-di-tert-butylphenol), 4,4′-bis(2,6-di-tert-butylphenol), 4,4′-bis(2-methyl-6-tert-butylphenol), 2,2′-methylene-bis(4-methyl-6-tert-butylphenol), 4,4′-butylidene-bis(3-methyl-6-tert-butylphenol), 4,4′-isopropylidene-bis(2,6-di-tert-butylphenol), 2,2′-methylene-bis(4-methyl-6-nonylphenol), 2,2′-isobutylidene-bis(4,6-dimethylphenol), 2,2′-5-methylene-bis(4-methyl-6-cyclohexylphenol), 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butyl-phenol, 2,6-di-tert-l-dimethylamino-p-cresol, 2,6-di-tert-4-(N,N′-di-methylaminomethylphenol), 4,4′-thiobis(2-methyl-6-tert-butylphenol), 2,2′-thiobis(4-methyl-6-tert-butylphenol), bis(3-methyl-4-hydroxy-5-tert-10-butylbenzyl)-sulfide, and bis(3,5-di-tert-butyl-4-hydroxybenzyl). Examples of alkylated and non-alkylated aromatic amines are alkylated diphenylamine, phenyl-alpha-naphthylamine, and alkylated-alpha-naphthylamine. Other classes of anti-oxidants are esters of thiodicarboxylic acids, salts of di-thiophosphoric acids, alkyl or aryl phosphates and molybdenum compounds, such as amine-molybdenum complex compound and molybdenum di-thiocarbamates may also be used as anti-oxidants, provided the molybdenum compounds do not include tri-nuclear molybdenum. However, their addition of the will contribute to the phosphorus, sulfur and sulfated ash content of the lubricating oil. 
       Low, Medium and High Overbased Metal Detergents 
       [0120]    Examples of the low and medium overbased metal detergents employed in the lubricating oil composition of the present invention are low, medium or high overbased sulfonates, salicylates, phenates or Mannich condensation products of alkylphenols, aldehydes and amines. These detergents may be alkali metal detergents or alkaline earth metal detergents. Preferably they are alkaline earth metal detergents and more preferably they are calcium detergents. The TBN of these detergents is greater than 1 and about 500, or more. These detergents are well known in the art and are commercially available. 
       Other Additives 
       [0121]    The lubricating oil composition of the present invention may also contain, in addition to the additives discussed above, other additives used to impart desirable properties to the lubricating oil composition of the present invention. Thus, the lubricating oil may contain one or more of additives, such as viscosity index improvers, pour point depressants, demulsifiers, extreme pressure agents and foam inhibitors. These additional additives are described in more detail below. 
       Viscosity Index Improvers 
       [0122]    Viscosity index improvers are added to lubricating oil to regulate viscosity changes due to the change in temperature. Some commercially available examples of viscosity index improvers are olefin copolymers, such as ethylene-propylene copolymers, styrene-isoprene copolymers, hydrated styrene-isoprene copolymers, polybutene, polyisobutylene, polymethacrylates, vinylpyrrolidone and methacrylate copolymers and dispersant type viscosity index improvers. 
       Extreme Pressure Agents 
       [0123]    Extreme pressure agents that may be used i the lubricating oil composition of the present invention include alkaline earth metal borated extreme pressure agents and alkali metal borated extreme pressure agents. Extreme pressure agents containing molybdenum may also be employed in the lubricating oil composition of the present invention, provided the molybdenum compounds do not include tri-nuclear molybdenum. Sulfurized olefins, zinc dialky-1-dithiophosphate (primary alkyl, secondary alkyl, and aryl type), di-phenyl sulfide, methyl tri-chlorostearate, chlorinated naphthalene, fluoroalkylpolysiloxane, lead naphthenate, neutralized or partially neutralized phosphates, di-thiophosphates, and sulfur-free phosphates. The preferred extreme pressure agents are those that will not contribute to the phosphorous content of the lubricating oil. 
       Pour Point Depressants 
       [0124]    Pour point depressants are additives that optimize the low temperatures fluidity of the lubricating oil. Examples are various copolymers. 
       Rust Inhibitors 
       [0125]    Rust inhibitors include nonionic polyoxyethylene surface active agents, such as polyoxyethylene lauryl ether, polyoxyethylene higher alcohol ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene octyl stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitol monostearate, polyoxyethylene sorbitol mono-oleate, and polyethylene glycol mono-oleate. Other compounds that may also be employed as rust inhibitors include stearic acid and other fatty acids, di-carboxylic acids, metal soaps, fatty acid amine salts, metal salts of heavy sulfonic acid, partial carboxylic acid ester of polyhydric alcohol, and phosphoric ester. However, preferred rust inhibitors are those that do not contribute to the phosphorus or sulfur content of the lubricating oil. Some of the above listed rust inhibitors may have friction modifying properties. However, these could be added in quantities sufficient for rust inhibition, but not high enough to provide their friction modifying property. 
       Corrosion Inhibitors 
       [0126]    Corrosion inhibitors are included in lubricating oils to protect vulnerable metal surfaces. Such corrosion inhibitors are generally used in very small amounts in the range of from about 0.02 weight percent to about 1.0 weight percent. Examples of corrosion inhibitors that may be used are sulfurized olefin corrosion inhibitor and the co-sulfurized alkenyl ester/alpha olefin corrosion inhibitor. 
       Metal Deactivators 
       [0127]    Metal deactivators that may be employed in the lubricating oil composition of the present invention include but are not limited to di-salicylidene propylenediamine, triazole derivatives, mercaptobenzothiazoles, thiodiazole derivatives, and mercaptobenzimidazoles. 
       Demulsifiers 
       [0128]    Addition product of alkylphenol and ethylene oxide, polyoxyethylene alkyl ether, and polyoxyethylene sorbitan ester may be employed in the lubricating oil composition of the present invention. 
       Foam Inhibitors 
       [0129]    Useful foam inhibitors for the present invention are alkyl methacrylate polymers, dimethyl silicone polymers and polysiloxane type foam inhibitors. 
         [0130]    For best overall results in terms of affording the properties desired in a conventional lubricating oil composition for lubricating diesel engines, gasoline engines and natural gas engines, the lubricating oil may contain a compatible combination of additives of each of the above classes of additives in effective amounts. 
         [0131]    The various additive materials or classes of materials herein described are well known materials and can be readily purchased commercially or prepared by known procedures or obvious modification thereof. 
         [0132]    In Table II below are given treatment rates for additives contemplated for use in the lubricating oil of the present invention. All component amounts are given as a weight percent of the active additive. 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE II 
               
               
                   
               
               
                   
                   
                   
                 Most 
               
               
                   
                   
                 Preferred 
                 Preferred 
               
               
                   
                 Range 
                 Range 
                 Range 
               
               
                 Component 
                 (wt %) 
                 (wt %) 
                 (wt %) 
               
               
                   
               
             
             
               
                 Borated Dispersant 
                 0 to 6 
                 1 to 5 
                 2 to 4 
               
               
                 Ethylene Carbonate 
                 2 to 8 
                 3 to 7 
                 4 to 6 
               
               
                 Treated Dispersant 
               
               
                 Low Overbased 
                   0 to 1.5 
                 0.5 to 1.5 
                 0.6 to 0.8 
               
               
                 Detergent 
               
               
                 Medium Overbased 
                 0 to 5 
                 0 to 3 
                 1.5 to 3   
               
               
                 Detergent 
               
               
                 High Overbased 
                   0 to 3.0 
                 0.4 to 2.5 
                 0.5 to 1.5 
               
               
                 Detergent 
               
               
                 Zinc Anti-wear 
                 0 to 2 
                 0.6 to 2   
                 1.0 to 1.8 
               
               
                 Di-phenylamine Anti- 
                 0 to 2 
                 0.2 to 1.5 
                 0.4 to 1.0 
               
               
                 oxidant 
               
               
                 Phenolic Anti-oxidant 
                 0 to 3 
                 0.2 to 2   
                 0.3 to 1.0 
               
               
                 Molybdenum Anti-oxidant 
                   0 to 2.0 
                   0 to 1.0 
                 0.1 to 0.5 
               
               
                 Foam Inhibitors 
                   0 to 0.5 
                   0 to 0.4 
                  0.1 to 0.35 
               
               
                   
               
             
          
         
       
     
       EXAMPLE 1 
       [0133]    Comparative Formulations A and B and Test Formulation C were prepared as described in Table II below. 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE III 
               
               
                   
               
               
                 Component 
                 Comparative 
                 Comparative 
                 Test 
               
               
                 (wt %) 
                 Formulation A 
                 Formulation B 
                 Formulation C 
               
               
                   
               
             
             
               
                 Base Oil 
                 Group II 
                 Group III 
                 Fischer- 
               
               
                   
                   
                   
                 Tropsch 
               
               
                   
                   
                   
                 Derived Base 
               
               
                   
                   
                   
                 Oil 
               
               
                 Borated Succinimide 
                 3.0 
                 3.0 
                 3.0 
               
               
                 Dispersant 
               
               
                 Ethylene Carbonate 
                 5 
                 5 
                 5 
               
               
                 Treated Succinimide 
               
               
                 Dispersant 
               
               
                 Low Overbased 
                 0.7 
                 0.7 
                 0.7 
               
               
                 Calcium 
               
               
                 Sulfonate Detergent 
               
               
                 Medium Overbased 
                 2.4 
                 2.4 
                 2.4 
               
               
                 Calcium Salicylate 
               
               
                 Detergent 
               
               
                 High Overbased 
                 0.9 
                 0.9 
                 0.9 
               
               
                 Sulfurized Calcium 
               
               
                 Phenate Detergent 
               
               
                 Zinc Di-thiophosphate 
                 1.6 
                 1.6 
                 1.6 
               
               
                 Anti-wear 
               
               
                 Di-phenylamine Anti- 
                 0.5 
                 0.5 
                 0.5 
               
               
                 oxidant 
               
               
                 Phenolic Anti-oxidant 
                 0.5 
                 0.5 
                 0.5 
               
               
                 Molybdenum 
                 0.4 
                 0.4 
                 0.4 
               
               
                 Succinimide 
               
               
                 Anti-oxidant 
               
               
                 Foam Inhibitors 
                 0.16 
                 0.16 
                 0.16 
               
               
                   
               
             
          
         
       
     
       EXAMPLE 2 
     Coefficient of Traction Measurements 
       [0134]    The ability to reduce the coefficient of traction of Text Formulation C was compared to Comparative Formulations A and B was evaluated as described below. 
         [0135]    Comparative Formulations A and B were compared with Test Formulation C in a series of Ball-on-Disk Rheometer experiments. As noted in Table II above, the three Formulations differ only in the selection of the base oils used to make the formulations. The rheometry experiments were designed to measure the traction coefficient under a variety of different conditions. The main variables were:
       1. Slide to Roll Ratio (SRR)—which varied from 25 to 50, and to 75.   2. Temperature—all measurements were conducted at a temperature of 100° C. and repeated at a temperature of 120° C.       
 
         [0138]    3. Pressure—was measured in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa.
       4. Contact speed—which was increased from just under 10 millimeters per second to well over 1000 millimeters per second.       
 
         [0140]    The SRR number represents the speed difference as a percentage of the average speed of the two surfaces, where both the disk speed and the ball speed are controlled individually. For any of the SRR values applied in the measurements, both surfaces are moving in the same direction but not at the same speed, thus creating a mixture of a sliding and a rolling motion. With increasing SRR values, the relative motion in the contact moves from rolling to sliding. For each of the combinations of conditions of SRR and temperature, the traction coefficient was measured as a function of the average contact speed, which was increased from just under 10 millimeters per second to well over 1000 millimeters per second. These measurements together make up a Stribeck Curve as shown in  FIG. 1 . A Stribeck Curve is a superimposition of two underlying curves. The first curve, X in  FIG. 1 , represents the reduction in friction between two surfaces that are in contact with increasing contact speed and the consequent build-up of an oil film. The second cure, Y in  FIG. 1 , represents the increase in the traction coefficient due to friction loss in the lubricant film itself when the film thickness increases with increasing contact speed. A comparison of measured points on the Stribeck curves in  FIG. 1  shows differences between Comparative Formulations A and B and Test Formulation C. 
         [0141]      FIGS. 2 ,  3 , and  4  show the traction coefficients measured at 100° C., in a configuration with a 19.05 mm diameter steel ball on a flat steel disk, both made of AISI-SAE 52100 steel with Young&#39;s Modulus of 207 GPa and Poisson Ratio 0.293, at an applied load of 10 Newton creating an average contact pressure of 433 Mpa and a maximum contact pressure of 649 MPa, for three different contact speeds and SRR of respectively 25, 50, and 75. While the traction coefficients for Comparative Formulation A containing Group II base oil and Comparative Formulation B containing Group III base oil are similar, the traction coefficients for Test Formulation C containing Fischer-Tropsch derived base oil are consistently lower, regardless of the contact speed. 
         [0142]    At the highest speed of 1000 millimeters per second, the contact is operating in the hydrodynamic lubrication regime. A reduction in the traction coefficient suggests a reduction in the frictional loss due to shearing in the lubricant film. Such a reduction would mostly impact the traction coefficient at higher contact speed, and would tend to increase the speed where the minimum traction coefficient is observed as Y′ in  FIG. 1 . 
         [0143]    In addition to seeing an impact at higher contact speeds, the data in this Example also show significant reductions in the traction coefficient at contact speeds of 100 millimeters per second and 10 millimeters per second. Given the higher traction coefficient at these speeds, it is concluded that the contact is operating in a mixed or boundary lubrication regime, where the frictional loss in the lubricant film itself is a negligible part of the traction coefficient. A reduction of the traction coefficient at low speeds suggests that Fischer-Tropsch derived base oil allows for reduced frictional loss due to metal-to-metal contact. Such a reduction in the traction coefficient at low speed would tend to decrease the speed where the minimum traction is observed as X′ in FIG. . 
         [0144]      FIG. 5  shows the traction coefficient as a function of average contact speed for the point where the traction coefficient reaches it minimum. Data points are shown for Comparative Formulations A and B and Test Formulation C containing Group II, Group III and Fischer-Tropsch derived base oil, respectively, for SRR 50 and 75. The graph clearly shows that the use of Fischer-Tropsch derived base oil in Test formulation C allows for both a reduction in the traction coefficient as well as a reduction of the speed where the contact transitions from hydrodynamic to boundary lubrication. This result with the use Fischer-Tropsch derived base oil, instead of use of the Group II or Group III, was unexpected. The surprising result observed in the data will have a very practical application in the development of new low friction engine oils.