Patent Publication Number: US-2018030368-A1

Title: Composition of continuously variable transmission oil for improving fuel efficiency and endurance performance

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims under 35 U.S.C. § 119(a) the benefit of Korean Patent Application No. 10-2016-0098006, filed on Aug. 1, 2016, the entire contents of which are incorporated herein by reference for all purposes. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a composition of continuously variable transmission oil for improving fuel efficiency and endurance performance. 
     Background Art 
     In recent years, for efficient use of energy and prevention of global warming, regulations on exhaust gases from automobiles such as carbon dioxide have been tightened. In order to respond to the environmental regulations, development of engine oil and transmission oil for improving fuel efficiency capable of reducing energy loss of the engine has been actively made. Particularly, when viscosity of the engine oil or transmission oil is lowered, energy which is lost by fluid resistance when power is transferred may be minimized. On the other hand, when the viscosity is lowered, thickness of an oil film is decreased and friction between metals is increased, and thus there is a disadvantage in endurance performance. 
     In the related art, a low-viscosity engine oil composition containing comb polymethacrylate (comb PMA) as a viscosity adjusting agent and polyalphaolefin (PAO) in base oil was used. The low-viscosity engine oil composition provides an improvement of fuel efficiency of the engine by lowering low-temperature viscosity. However, the fuel efficiency improvement is negligible when being applied to a continuously variable transmission. 
     As for oil for continuously variable transmission, it is important to provide oil capable of improving fuel efficiency through reduction of fluid resistance by lowering the low-temperature viscosity and enhancing endurance performance of the transmission by increasing high-temperature viscosity. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE DISCLOSURE 
     The present invention has been made in an effort to solve the above-described problems associated with prior art. 
     As a result, the inventors of the present invention discovered that an oil composition including a predetermined amount of olefin amide comb PMA as a viscosity adjusting agent in base oil having a pour point of −40° C. or less can be used as continuously variable transmission oil. The oil composition provides an improvement of fuel efficiency through reduction of fluid resistance by decreasing viscosity at a low temperature and an enhancement of endurance performance of the transmission by increasing the viscosity at a high temperature, and then completed the present invention. 
     Therefore, the present invention has been made in an effort to provide a novel composition of continuously variable transmission oil that can improve fuel efficiency by decreasing viscosity at a low temperature and enhance endurance performance by increasing viscosity at a high temperature. 
     In one aspect, the present invention provides a composition of continuously variable transmission oil including about 75 wt % to about 85 wt % of base oil having a pour point of about −40° C. or less; about 5 wt % to about 15 wt % of olefin amide comb PMA as a viscosity adjusting agent; about 8 wt % to 15 wt % of an anti-wear additive; and about 2 wt % to about 5 wt % of a friction modifier. 
     The composition of continuously variable transmission oil according to the present invention can improve fuel efficiency by decreasing viscosity at a low temperature and enhance endurance performance by increasing viscosity at a high temperature. 
     Other aspects and preferred embodiments of the invention are discussed infra. 
     It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. 
     The above and other features of the invention are discussed infra. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated in the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1A  illustrates chain structures of comb polymethacrylate (comb PMA) and asteric polymethacrylate (asteric PMA) as viscosity adjusting agents in the related art and  FIG. 1B  illustrates a chain structure of olefin amide comb PMA used in the present invention. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
     In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
     DETAILED DESCRIPTION 
     Hereinafter reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     A composition of continuously variable transmission oil of the present invention comprises base oil having a pour point of about −40° C. or less (e.g., about −40° C., about −45° C., about −50° C., about −55° C., about −60° C., about −65° C., about −66° C., or less), olefin amide comb PMA as a viscosity adjusting agent, and an anti-wear additive. The viscosity adjusting agent as a viscosity adjusting agent (OACP, hereinafter, referred to as olefin amide comb PMA) having a polar chain introduced with an amide group improves a viscosity index (VI) characteristic for the temperature of the composition of continuously variable transmission oil by maximizing low-temperature shrinkage and high-temperature expansion for a temperature due to introduction of a polar group. 
     In the related art, as the viscosity adjusting agent, comb polymethacrylate (comb PMA) and asteric polymethacrylate (asteric PMA) are used ( FIG. 1A ). In the present invention, a polar value varies by introducing a side chain in which an amide group is introduced in a main chain of comb PMA to maximize low-temperature shrinkage and high-temperature expansion for the temperature ( FIG. 1B ). 
     In detail, the composition of continuously variable transmission oil according to the present invention comprises about 75 wt % to 85 wt % (e.g., about 75 wt %, 76 wt %, 77 wt %, 78 wt %, 79 wt %, 80 wt %, 81 wt %, 82 wt %, 83 wt %, 84 wt %, or about 85 wt %) of base oil having a pour point of −40° C. or less (e.g., about −40° C., about −45° C., about −50° C., about −5° C., about −60° C., about −65° C., about −66° C., or less); about 5 wt % to 15 wt % (e.g., about 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, or about 15 wt %) of olefin amide comb PMA as a viscosity adjusting agent; about 8 wt % to about 15 wt % (e.g., about 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, or about 15 wt %) of an anti-wear additive; and about 2 wt % to about 5 wt % (e.g., about 2 wt %, 3 wt %, 4 wt %, or about 5 wt %) of a friction modifier. 
     Respective components configuring the composition of continuously variable transmission oil according to the present invention will be described below in more detail. 
     The base oil used in the present invention means a lubricant which has a pour of −40° C. or less and is used for lubrication of a gear and has functions of preventing between gear surfaces and preventing the gear surfaces from being melted and attached by reducing friction and wear. When the pour point of the base oil is greater than −0° C., there a limitation of worsening low-temperature fluidity due to precipitation of a wax and thus the base oil is used within the range. The base oil having the lowest pour point among the exiting base oils is polyalphaolefin (PAO) of −69° C., and in the present as the base oil having the pour point of −40° C. or less (e.g., about −40° C., about −45° C., −50° C., about −55° C., about −60° C., about −65° C., about −66° C., or less), at least one selected from the group consisting of polyalphaolefin (PAO) and base oil including a hydrocarbon compound may be used. The base oil including the paraffin-based hydrocarbon compound is the group which belongs to group III classified in the American Petroleum Institute (API) and may representatively use products of Yubase 3, Yubase L3, and Ultra S3. 
     In this case, the base oil may be used with about 75 wt % to 85 wt % (e.g., about 75 wt %, 76 wt %, 77 wt %, 78 wt %, 79 wt %, 80 wt %, 81 wt %, 82 wt %, 83 wt %, 84 wt %, or about 85 wt %). In the case of less than 75 wt %, other viscosity adjusting agents and additives are added with a large amount and thus, there is a limitation of worsening endurance performance such as a reduction of a friction coefficient. In the case of greater than 85 wt %, used amounts of other viscosity adjusting agents and additives are limited and thus there is a limitation of worsening fuel efficiency and endurance performance. Thus, the base oil may be used within the range. 
     The viscosity adjusting agent used in the present invention may be used with about 5 wt % to about 15 wt % (e.g., about 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, or about 15 wt %) with respect to the entire weight of the continuously variable transmission oil as olefin amide comb polymethacrylate (OACP). When the OACP is less than 5 wt %, a viscosity reduction effect is low and a fuel efficiency improvement effect is slight, and when the OACP is greater than 15 wt %, low-temperature viscosity at −40° C. is increased to have a bad effect on low-temperature operability and thus it is preferred that the OACP is used within the range. 
     In detail, the OACP used in the present invention has a structure of the following Chemical Formula 1. 
     
       
         
         
             
             
         
       
     
     Chemical Formula 1 includes a lactam structure, and R 1  is a straight or branched chain alkyl group of C 1  to C 20 , R 2  is olefin oligomer and has a straight or branched chain alkenyl group of C 2  to C 40 , a ratio of X to Y is 1:2 to 1:3, and a weight-average molecular weight is about 100,000 to about 150,000. 
     The OACP of the present invention may be included with about 5 wt % to about 15 wt % (e.g., about 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, or about 15 wt %) with respect to the entire weight. When the OACP is less than 5 wt %, there is a limitation in viscosity reduction and thus there is no fuel efficiency improvement effect, and when the OACP is greater than 15 wt %, the low-temperature viscosity at −40° C. is rapidly increased and thus there is a limitation in low-temperature operability. Thus, it is preferred that the OACP is used within the range. 
     Meanwhile, in the related art, comb PMA having a structure of the following Chemical Formula 2 is used as a viscosity adjusting agent and a polar side chain is not introduced as illustrated in  FIG. 1 . 
     
       
         
         
             
             
         
       
     
     In Chemical Formula 2, R 1  is a straight or branched chain alkyl group of C 1  to C 20 , R 2  is olefin oligomer and has a straight or branched chain alkenyl group of C 2  to C 40 , a ratio of X to Y is 1:2 to 1:3, and a weight-average molecular weight is about 400,000 to about 500,000. 
     As another viscosity adjusting agent in the related art, asteric PMA has a structure of the following Chemical Formula 3 and a weight-average molecular weight of about 200,000 to about 300,000. In this case, R 1  is a straight or branched chain alkyl group of C 1  to C 20 . 
     
       
         
         
             
             
         
       
     
     In the present invention, a side chain in which an amide group is introduced in a main chain of the comb PMA is introduced and a polar value varies to maximize low-temperature shrinkage and high-temperature expansion for the temperature, thereby improving fuel efficiency by decreasing low-temperature viscosity of the continuously variable transmission oil and enhancing endurance performance by increasing high-temperature viscosity. 
     The anti-wear additive used in the present invention serves to maintain endurance performance by dispersing foreign substances in the oil and prevent deterioration of endurance performance caused by wear between gears and may be used with about 8 wt % to about 15 wt % (e.g., about 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, or about 15 wt %) with respect to the entire oil weight. When the additive is less than 8 wt %, there is a limitation in maintaining the endurance performance, and when the additive is greater than 15 wt %, the endurance performance may be decreased due to deterioration of a friction coefficient caused by adding a large amount of additive and thus it is preferred that the additive is used within the range. 
     As the anti-wear additive of the present invention, it is preferred that at least one selected from the group consisting of dibutyl hydrogen phosphite, amine phosphite, and isobutynyl succinic ester is used. More preferably, dibutyl hydrogen phosphite is used. In the case of using dibutyl hydrogen phosphite-based additive, there is an advantage in maintaining a belt pulley friction coefficient of the continuously variable transmission. 
     The present invention may further include about 2 wt % to 5 wt % (e.g., about 2 wt %, 3 wt %, 4 wt %, or about 5 wt %) of a friction modifier with respect to the entire continuously variable transmission oil weight. When the friction modifier is less than 2 wt %, a kinetic/static friction coefficient of transmission is decreased and thus anti-wear deteriorates, and when the friction modifier is greater than 5 wt %, friction between metals is increased and thus there is a limitation in endurance performance. Thus, it is preferred that the friction modifier is used within the range. The friction modifier of the present invention may use at least one selected from the group consisting of sulfurized fatty ester, alkenyl phosphite, and polyol ester. 
     As general additives of the present invention, an antioxidant, an anti-foam agent, and the like may be further included. The antioxidant is used for preventing oxidation of engine oil. The antioxidant may use amine-based antioxidants such as 3-hydroxydiphenyl amine and phenyl-alpha-naphthylamine and may be included in a range of about 0.05 wt % to about 3 wt % (e.g., about 0.05 wt %, 0.1 wt %, 0.2 wt %, 0.3 wt %, 0.4 wt %, 0.5 wt %, 0.6 wt %, 0.7 wt %, 0.8 wt %, 0.9 wt %, 1 wt %, 1.5 wt %, 2 wt %, 2.5 wt %, or about 3 wt %) in composition of the present invention. When the content thereof is less than 0.05 wt %, anti-oxidation performance may be decreased and when the content is greater than 3 wt %, side effects such as competitive adsorption and metal corrosion may occur. 
     As the anti-foam agent, at least one selected from the group consisting of silicon and polymethacrylate is included. The anti-foam agent may be included in a range of from about 0.0005 wt % to about 2 wt % (e.g., about 0.0005 wt %, 0.001 wt %, 0.005 wt %, 0.01 wt %, 0.05 wt %, 0.1 wt %, 0.2 wt %, 0.3 wt %, 0.4 wt %, 0.5 wt %, 0.6 wt %, 0.7 wt %, 0.8 wt %, 0.9 wt %, 1 wt %, 1.1 wt %, 1.2 wt %, 1.3 wt %, 1.4 wt %, 1.5 wt %, 1.6 wt %, 1.7 wt %, 1.8 wt %, 1.9 wt %, or 2 wt %) in the composition of the present invention. When the content thereof is less than 0.0005 wt %, there is a problem in that the occurrence of bubbles in the lubricant cannot be efficiently suppressed, and when the content is greater than 2 wt %, there is a problem in that an anti-foam property is rather decreased or the anti-foam agent is precipitated in the lubricant. 
     Accordingly, in the continuously variable transmission oil according to the present invention, olefin amide comb PMA as a polar group in the base oil having a pour point of −40° C. or less is used as the viscosity adjusting agent to improve flexibility and expansion of a polar chain and a non-polar chain, thereby maximizing low-temperature shrinkage and high-temperature expansion and enhancing fuel efficiency and endurance performance of the continuously variable transmission. 
     As described above, the present invention will be described in more detail based on the following Examples and the present invention is not limited thereto. 
     EXAMPLES 
     The following examples illustrate the invention and are not intended to limit the same. 
     Examples 1 to 5 and Comparative Examples 1 to 7 
     Preparation of Composition of Continuously Variable Transmission Oil 
     Components listed in the following Table 1 were put into a reactor and mixed under conditions of a temperature of 40° C. and a velocity of a stirrer of 1,000 rpm to prepare a composition of continuously variable transmission oil. 
     [Respective Components Configuring Composition of Continuously Variable Transmission Oil] 
     Base oil: Yubase L3 having pour point of −40° C. (Group III, product manufactured by SK Corporation) 
     Viscosity adjusting agent: {circle around (1)} Olefin Amide Comb PMA: A ratio of X to Y is 1:2, an amide monomer is included with 10 to 50 wt %, and a weight-average molecular weight is 150,000, {circle around (2)} Comb PMA: Product manufactured by Rohmax Corporation, {circle around (3)} Asteric PMA: Product manufactured by Lubrizol Corporation 
     Clean dispersing and anti-wear additives: Dibutyl hydrogen phosphite (product manufactured by Lubrizol Corporation) 
     Friction modifier: Sulfurized fatty ester (product manufactured by Lubrizol Corporation) 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Comparative Example 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 1 
                   
               
               
                 Classification 
                   
                 (current 
               
               
                 (wt %) 
                 Examples 
                 specification) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Base 
                 Yubase L3 
                 85 
                 83 
                 80 
                 78 
                 75 
                 82 
                 87 
                 73 
                 85 
                 80 
                 85 
                 80 
               
               
                 oil 
                 (pour point 
               
               
                   
                 of −40° C.) 
               
               
                 Viscosity 
                 Olefin 
                 5 
                 7 
                 10 
                 12 
                 15 
                 — 
                 3 
                 17 
                 — 
                 — 
                 — 
                 — 
               
               
                 adjusting 
                 amide 
               
               
                 agent 
                 comb 
               
               
                   
                 polymethacrylate 
               
               
                   
                 (OACP) 
               
               
                   
                 Comb 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 5 
                 10 
               
               
                   
                 polymethacrylate 
               
               
                   
                 (comb 
               
               
                   
                 PMA) 
               
               
                   
                 Asteric 
                 — 
                 — 
                 — 
                 — 
                 — 
                 8 
                 — 
                 — 
                 5 
                 10 
                 — 
                 — 
               
               
                   
                 polymethacrylate 
               
               
                   
                 (Asteric 
               
               
                   
                 PMA) 
               
               
                 Anti- 
                 Dibutyl 
                 8 
                 8 
                 8 
                 8 
                 8 
                 8 
                 8 
                 8 
                 8 
                 8 
                 8 
                 8 
               
               
                 wear 
                 hydrogen 
               
               
                 additive 
                 phosphite 
               
               
                 Friction 
                 Sulfurized 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                 modifier 
                 fatty 
               
               
                   
                 ester 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Total content 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
               
               
                   
               
            
           
         
       
     
     Examples 6 to 7 and Comparative Examples 8 to 14 
     Preparation of Composition of Continuously Variable Transmission Oil 
     Components illustrated in the following Table 2 were put into a reactor and mixed under conditions of a temperature of 60° C. and a velocity of a stirrer of 1,000 rpm to prepare a composition of continuously variable transmission oil. 
     [Respective Components Configuring Composition of Continuously Variable Transmission Oil] 
     Base oil: {circle around (1)} Yubase L3 having pour point of −40° C. (Group III, product manufactured by SK Corporation), {circle around (2)} PAO4 having pour point of −69° C. (product manufactured by Chevron Philips Corporation), {circle around (3)} Kixx4 having pour point of −30° C. (Group III, product manufactured by GS Caltex Corporation) 
     Viscosity adjusting agent: Olefin Amide Comb PMA: A ratio of X to Y is 1:2, an amide monomer is included with 10 to 50 wt %, and a weight-average molecular weight is 150,000. 
     Anti-wear additives: Dibutyl hydrogen phosphite (product manufactured by Lubrizol Corporation) 
     Friction modifier: Sulfurized fatty ester (product manufactured by Lubrizol Corporation) 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
             
            
               
                   
                   
               
               
                   
                 Example 
                 Comparative Example 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Classification (wt %) 
                 6 
                 8 
                 9 
                 10 
                 11 
                 12 
                 13 
                 14 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Base oil 
                 Yubase L3 (pour 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                   
                 point of −40° C.) 
               
               
                   
                 PAO4 (pour point of −69° C.) 
                 80 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                   
                 Kixx4 (pour point of −30° C.) 
                 — 
                 87 
                 85 
                 83 
                 80 
                 77 
                 75 
                 73 
               
               
                 Viscosity 
                 Olefin amide comb 
                 10 
                 3 
                 5 
                 7 
                 10 
                 13 
                 15 
                 17 
               
               
                 adjusting agent 
                 polymethacrylate 
               
               
                   
                 (OACP) 
               
               
                 Anti-wear 
                 Dibutyl hydrogen 
                 8 
                 8 
                 8 
                 8 
                 8 
                 8 
                 8 
                 8 
               
               
                 additive 
                 phosphite 
               
               
                 Friction 
                 Sulfurized fatty ester 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                 modifier 
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Total content 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
               
               
                   
               
            
           
         
       
     
     TEST EXAMPLES 
     In the respective compositions for continuously variable transmission oil prepared in Examples 1 to 5 and Comparative Examples 1 to 7 and Examples 3 and 6 and Comparative Examples 1 to 14, performance was tested based on a performance test method which is widely known and the result thereof was listed in the following Tables 3 and 4. 
     [Performance Test Method] 
     Kinematic viscosity of 40° C./100° C. (cSt): measured by ASTM D 445 method. 
     Low-temperature viscosity of −40° C. (cP): measured by ASTM D 2983 method. 
     Fuel efficiency improvement ratio (automotive fuel coefficient, %): evaluated by FTP75 (authentication mode). 
     
       
         
           
               
               
             
               
                   
                 TABLE 3 
               
             
            
               
                   
                   
               
               
                   
                 Comparative Example 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 1 
                   
               
               
                   
                 Example 
                 (current 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Evaluation item 
                 1 
                 2 
                 3 
                 4 
                 5 
                 specification) 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 40° C. 
                 23 
                 22 
                 20 
                 19 
                 18 
                 25 
                 24 
                 17 
                 26 
                 25 
                 24 
                 23 
               
               
                 Kinematic 
               
               
                 viscosity (cSt) 
               
               
                 100° C. 
                 5.8 
                 6.2 
                 7.0 
                 7.1 
                 7.2 
                 5.4 
                 5.5 
                 7.3 
                 5.3 
                 5.5 
                 5.5 
                 5.7 
               
               
                 Kinematic 
               
               
                 viscosity (cSt) 
               
               
                 −40° C. 
                 6500 
                 6500 
                 7000 
                 9000 
                 10000 
                 8500 
                 8300 
                 15000 
                 9000 
                 9500 
                 12000 
                 13000 
               
               
                 low- 
               
               
                 temperature 
               
               
                 viscosity (cP) 
               
               
                 Fuel efficiency 
                 0.1 
                 0.3 
                 0.4 
                 0.2 
                 0.2 
                 Reference 
                 0 
                 0.1 
                 −0.1 
                 0 
                 0 
                 0.1 
               
               
                 improvement 
               
               
                 ratio (%) 
               
               
                   
               
            
           
         
       
     
     In Table 3, in the case of Examples 1 to 5 according to the present invention, it can be seen that there is a fuel efficiency improvement effect through reduction of fluid resistance by decreasing viscosity at a temperature range (20 to 85° C.) for measuring fuel efficiency. Particularly, in the case of Example 3, the most excellent fuel efficiency improvement ratio is shown. 
     Meanwhile, in the case of Comparative Example 2 in which olefin amide comb PMA is less than 5 wt % and Comparative Example 3 in which the olefin amide comb PMA is greater than 15 wt %, it can be seen that a viscosity reduction effect is low and thus the fuel efficiency improvement effect is slight. 
     In the case of Comparative Examples 4 to 7 using asteric PMA or comb PMA used as the viscosity adjusting agent in the related art, it can be seen that the fuel efficiency improvement effect is slight or −40° C. low-temperature viscosity is increased and thus the fuel efficiency is not good. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 4 
               
             
            
               
                   
                   
               
               
                   
                 Example 
                 Comparative Example 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Evaluation item 
                 3 
                 6 
                 8 
                 9 
                 10 
                 11 
                 12 
                 13 
                 14 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 40° C. Kinematic 
                 20 
                 19 
                 24 
                 23 
                 22 
                 22 
                 21 
                 20 
                 20 
               
               
                 viscosity (cSt) 
               
               
                 100° C. Kinematic 
                 7.0 
                 7.0 
                 5.5 
                 6.0 
                 6.8 
                 6.9 
                 7.2 
                 7.3 
                 7.5 
               
               
                 viscosity (cSt) 
               
               
                 −40° C. low-temperature 
                 7000 
                 5500 
                 13000 
                 15000 
                 17000 
                 20000 
                 25000 
                 27000 
                 29000 
               
               
                 viscosity (cP) 
               
               
                 Fuel efficiency 
                 0.4 
                 0.6 
                 0 
                 0 
                 0 
                 −0.1 
                 −0.1 
                 −0.1 
                 −0.1 
               
               
                 improvement ratio (%) 
               
               
                   
               
            
           
         
       
     
     In Table 4, like Comparative Examples 8 to 14, in the case of using olefin amide comb PMA as a general base oil having a pour point of −30° C., it can be seen that −40° C. low-temperature viscosity is rather increased and thus the fuel efficiency is decreased. 
     Meanwhile, in the case of Example 6 using polyalphaolefin (PAO) having a pour point of −69° C. as a base oil, it can be seen that the fuel efficiency improvement ratio is improved to 0.6%. The reason is that the viscosity adjusting agent used in the present invention is less crystallized in the PAO which is a wax component at a low temperature to prevent an increase in viscosity. 
     Therefore, the composition of continuously variable transmission oil in the present invention can be provided as continuously variable transmission oil with improved fuel efficiency by decreasing low-temperature viscosity and enhanced endurance performance by increasing high-temperature viscosity by using olefin amide comb PMA which is a new viscosity adjusting agent in base oil having a pour point of −40° C. or less. 
     The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.