Automotive lubricant composition

Abstract

Lubricant compositions for use in automotive engine oils comprising a combination of a specific base stock or mixture of base stocks and a friction reducing additive to improve fuel economy and fuel economy longevity of the automotive engine oil. The friction reducing additive is a specific partial polyol ester and may also include a specific saturated primary amide.

1 . A lubricant composition for use in an automotive engine oil comprising 
 (A) a base stock which comprises as a major component at least one of a Group III, Group IV and Group VI base stock wherein the Group nomenclatures are as defined by the American Petroleum Institute;    (B) 0.01-5% of a partial polyol ester friction reducing additive derived from the reaction of either glycerol or trimethylolpropane with a monocarboxylic acid of formula R 1 COOH, where R 1  is a straight or branched chain aliphatic hydrocarbon group with 12-22 carbon atoms, the monocarboxylic acid having an iodine value of not more than 20 and a cloud point of not more than 45° C.; and    (C) optionally 0.01-5% of a saturated primary amide friction reducing additive of formula R 2 CONH 2  where R 2  is a straight or branched chain aliphatic hydrocarbon group with 12-22 carbon atoms;    wherein the oxidative induction time of the friction reducing additive in (B), together with the friction reducing additive in (C) if present, is at least 25 minutes, said oxidative induction time being measured using a high pressure differential scanning calorimeter after carrying out the steps comprising placing 5 mg of the friction reducing additive with 0.5% by weight of a phenolic antioxidant having a thioether group relative to the friction reducing additive in a 40 μl aluminium crucible and heating the calorimeter from 30° C. to 170° C. at a rate of 50° C./min followed by maintenance of the temperature at 170° C. with an air pressure of 40 bar and air flow of 50 ml/min.    
   
   
       2 . A lubricant composition according to  claim 1 , wherein the base stock comprises at least one of a Group III or Group IV base stock.  
   
   
       3 . A lubricant composition according to  claim 2 , wherein the base stock comprises a Group III base stock.  
   
   
       4 . A lubricant composition according to  claim 2 , wherein the major component of the base stock is at least 65% of the base stock.  
   
   
       5 . A lubricant composition according to  claim 2 , wherein the Group III and Group IV base stocks each individually have a viscosity at 100° C. of 3 to 10 mm 2 /s, a viscosity index of at least 120 and a Noack evaporation loss of less than 20%.  
   
   
       6 . A lubricant composition according to  claim 2 , wherein the Group III and Group IV base stocks each individually have a viscosity at 100° C. of 4 to 8 mm 2 /s, a viscosity index of at least 125 and a Noack evaporation loss of less than 15%.  
   
   
       7 . A lubricant composition according to  claim 1 , further comprising as a minor component less than 30% of any or a mixture of Group I, II and/or Group V base stocks and/or any or a mixture of Group III, Group IV and Group VI base stocks which have not been used as the major component in the base stock.  
   
   
       8 . A lubricant composition according to  claim 1 , further comprising as a minor component less than 15% of a viscosity index improver, itself having a viscosity at 100° C. of 20 to 4000 mm 2 /s.  
   
   
       9 . A lubricant composition according to  claim 1 , where the base stock is a mixture of 70 to 95% by weight Group III with 0 to 20% Group V alkyl naphthalene or ester and 2 to 10% high viscosity polyalphaolefin.  
   
   
       10 . A lubricant composition according to  claim 1 , where the base stock is a mixture of 60 to 90% by weight Group IV with 5 to 20% Group V alkyl naphthalene or ester and 2 to 10% high viscosity polyalphaolefin.  
   
   
       11 . A lubricant composition according to  claim 1 , wherein the partial polyol ester is the reaction product of either glycerol or trimethylolpropane with a C14-C18 monocarboxylic acid having an iodine value of not more than 10 and a cloud point of not more than 45° C. wherein the product ester is a monoester or diester or a mixture thereof.  
   
   
       12 . A lubricant composition according to  claim 11 , wherein the partial polyol ester is present at a level of 0.01 to 5% in the lubricant composition.  
   
   
       13 . A lubricant composition according to  claim 11 , wherein the partial polyol ester is present at a level of 0.01 to 2% in the lubricant composition.  
   
   
       14 . A lubricant composition according to  claim 1 , wherein, when present, the saturated primary amide is isostearylamide.  
   
   
       15 . A lubricant composition according to  claim 1 , wherein, when present, the saturated primary amide is present at a level of 0.01 to 5% in the lubricant composition.  
   
   
       16 . A lubricant composition according to  claim 15 , wherein, when present, the saturated primary amide is present at a level of 0.01 to 2% in the lubricant composition.  
   
   
       17 . A lubricant composition according to  claim 1 , wherein when the saturated primary amide is present, the ratio of partial polyol ester to saturated primary amide ranges from 95:5 wt % to 5:95 wt %.  
   
   
       18 . A lubricant composition according to  claim 1 , wherein when the saturated primary amide is present, the ratio of partial polyol ester to saturated primary amide ranges from 80:20 wt % to 20:80 wt %.  
   
   
       19 . A lubricant composition according to  claim 1 , wherein when the saturated primary amide is present the friction reducing additive is 0.5% partial polyol ester with 0.5% saturated primary amide.  
   
   
       20 . A lubricant composition according to  claim 1 , wherein the oxidative induction time of the friction reducing additive in (B), together with (C) if present, is at least 30 minutes.  
   
   
       21 . A lubricant composition according to  claim 20 , wherein the oxidative induction time of the friction reducing additive in (B), together with (C) if present, is at least 35 minutes.  
   
   
       22 . A lubricant composition according to  claim 1 , further comprising other additives at levels between 5 to 20% by weight of the total weight of the lubricant composition.  
   
   
       23 . A method of lubricating an automotive engine oil using a lubricant composition comprising 
 (A) a base stock which comprises as a major component at least one of a Group III, Group IV and Group VI base stock wherein the Group nomenclatures are as defined by the American Petroleum Institute;    (B) 0.01-5% of a partial polyol ester friction reducing additive derived from the reaction of either glycerol or trimethylolpropane with a monocarboxylic acid of formula R 1 COOH, where R 1  is a straight or branched chain aliphatic hydrocarbon group with 12-22 carbon atoms, the monocarboxylic acid having an iodine value of not more than 20 and a cloud point of not more than 45° C.; and    (C) optionally 0.01-5% of a saturated primary amide friction reducing additive of formula R 2 CONH 2  where R 2  is a straight or branched chain aliphatic hydrocarbon group with 12-22 carbon atoms;    wherein the oxidative induction time of the friction reducing additive in (B), together with the friction reducing additive in (C) if present, is at least 25 minutes, said oxidative induction time being measured using a high pressure differential scanning calorimeter after carrying out the steps comprising placing 5 mg of the friction reducing additive with 0.5% by weight of a phenolic antioxidant having a thioether group relative to the friction reducing additive in a 40 μl aluminium crucible and heating the calorimeter from 30° C. to 170° C. at a rate of 50° C./min followed by maintenance of the temperature at 170° C. with an air pressure of 40 bar and air flow of 50 ml/min.