Lubricant compositions having improved rates of air release

Abstract

The air release rate of lubricating compositions is significantly enhanced when the composition is formulated with alkyl salicylate detergents, especially calcium or magnesium alkyl salicylate detergents. Compositions having the improved air release rates are substantially free of a viscoelastic fluid having a shear stress greater than 11 kPa and a viscosity greater than 30 cSt at 100° C.

1 . A method for improving the air release rate of a lubricating composition comprising a major amount of a lubricating base oil and one or more detergents, the method comprising using as the one or more detergents an alkyl salicylate detergent.  
   
   
       2 . The method of  claim 1  wherein the one or more alkyl salicylate detergents are used in an amount sufficient to provide the composition with a TBN in the range of about 4 to about 8.  
   
   
       3 . The method of  claim 2  wherein the alkyl salicylate detergent is an alkaline earth metal alkyl salicylate.  
   
   
       4 . The method of  claim 3  wherein the alkaline earth metal is calcium.  
   
   
       5 . The method of  claim 3  wherein the alkaline earth metal is magnesium.  
   
   
       6 . The method of  claim 2  wherein the alkyl salicylate detergent is an ashless nitrogen-containing detergent.  
   
   
       7 . A lubricating composition comprising: 
 (a) a major amount of an oil of lubricating viscosity,    (b) one or more salicylate detergents in an amount sufficient to provide the composition with a TBN in the range of about 4 to about 8, and    (c) a minor amount of one or more lubricant additives,    the composition having less than about 0.8 wt % sulfated ash and being substantially free of a viscoelastic fluid, said fluid having both a shear stress greater than 11 kPa and a kinematic viscosity greater than 30 cSt at 100° C.    
   
   
       8 . The composition of  claim 7  wherein the salicylate detergent is an alkali or alkaline earth metal salt of an alkyl salicylic acid having one or more alkyl groups of at least 8 carbon atoms.  
   
   
       9 . The composition of  claim 8  wherein the salicylate detergent is a calcium salicylate.  
   
   
       10 . The composition of  claim 9  wherein the composition has a TBN of from 5 to 7.  
   
   
       11 . The composition of  claim 10  wherein the calcium salicylate detergent comprises a mixture of calcium salicylates, one having a TBN greater than 200, a second having a TBN of about 100 to 200 and a third having a TBN of less than 100.  
   
   
       12 . The composition of  claim 7  wherein the salicylate detergent is an ashless salicylate detergent.  
   
   
       13 . The composition of claims  8  and  12  wherein the composition has a sulfur content less than about 0.25 wt % based on the total weight of the composition.  
   
   
       14 . A lubricating composition comprising: 
 (a) greater than 50 wt % of a base oil of lubricating viscosity comprising one or more oils selected from Group II, Group III (including GTL), Group IV and Group V base stocks; and    (b) one or more detergents selected from sulfur-free alkyl salicylate detergents in an amount to provide the oil of lubricating viscosity with a TBN of from about 4 to about 8;    (c) one or more lubricant performance enhancing additives,    the composition having less than 0.8 wt % sulfated ash and being free of a viscoelastic fluid having both a shear stress greater than 11 kPa and a kinematic viscosity greater than 30 cSt at 100° C.    
   
   
       15 . The composition of  claim 14  wherein the detergent is a calcium alkyl salicylate detergent.  
   
   
       16 . In the lubrication of an engine with a crankcase lubricant wherein the lubricant additionally is used to perform a hydraulic function, the improvement comprising using as the crankcase lubricant the composition of any one of  claims 7  to  15 .  
   
   
       17 . The use of one or more alkyl salicylate detergents to improve the air release rate of a lubricating composition.  
   
   
       18 . The use according to  claim 17 , wherein the lubricating composition comprises at least 50 wt % of an oil of lubricating viscosity, based on the total weight of the lubricating composition.  
   
   
       19 . The use according to any of claims  17  or  18 , wherein the lubricating composition comprises 1 wt % to 6 wt % alkyl salicylate detergent, based on the total weight of the lubricating composition.  
   
   
       20 . The use according to any of  claims 17  to  19 , wherein the alkyl salicylate detergent is an alkaline earth metal salicylate detergent, preferably a calcium or magnesium salicylate detergent.  
   
   
       21 . The use according to any of  claims 17  to  20 , wherein the alkyl salicylate detergent is an ashless nitrogen-containing detergent.