Lubricant Compositions With Low HTHS for a Given SAE Viscosity Grade

Abstract

A lubricant composition that exhibits low high temperature high shear viscosity is disclosed. The lubricant composition is made up of a first polymer having a kinematic viscosity ratio less than or equal to 0.25 and a shear stability index (SSI) equal to or greater than 20 percent and base oil having a viscosity index equal to or greater than 120.

1 . A lubricant composition comprising:
 a first polymer having a kinematic viscosity ratio less than or equal to 0.25 and a shear stability index (SSI) equal to or greater than 20 percent; and   base oil having a viscosity index equal to or greater than 120.   
   
   
       2 . A lubricant composition according to  claim 1  where the first polymer comprises a minimum of 5 weight percent styrene. 
   
   
       3 . A lubricant composition according to  claim 1  where the first polymer comprises a normal block copolymer (i.e., true block copolymer) or a random block copolymer. 
   
   
       4 . A lubricant composition according to  claim 1  further comprising a second polymer. 
   
   
       5 . A lubricant composition according to  claim 4  wherein the second polymer is selected from a group comprising olefin polymers; hydrogenated polymers and copolymers and terpolymers of styrene with isoprene and/or butadiene; polymers of alkyl acrylates or alkyl methacrylates; copolymers of alkyl methacrylates with N-vinyl pyrrolidone or dimethylaminoalkyl methacrylate; post-grafted polymers of ethylenepropylene with an active monomer such as maleic anhydride; styrene-maleic anhydride polymers post-reacted with alcohols and amines. 
   
   
       6 . A lubricant composition according to  claim 1  comprising a detergent inhibitor package comprising one or more of the following: metal or ash-containing detergents, antioxidants, anti-wear agents, rust inhibitors, anti-foaming agents, demulsifiers, rust inhibitors, ashless detergents and pour point depressants. 
   
   
       7 . A lubricant composition according to  claim 6  having a concentration of phosphorus less than 0.08 weight percent. 
   
   
       8 . A lubricant composition according to  claim 6  having a concentration of sulfur less than 0.5 weight percent. 
   
   
       9 . A lubricant composition according to  claim 6  having a concentration of chlorine less than 150 PPM. 
   
   
       10 . A lubricant composition according to  claim 6  having an ash content ranging from 0.35 to 2 mass percent. 
   
   
       11 . A lubricant composition according to  claim 1  that satisfies the requirements for SAE J300 viscosity grade 0Wx or 5Wx where x is 10, 20, 30 or 40. 
   
   
       12 . A lubricant composition comprising:
 a polymer having a kinematic viscosity ratio less than or equal to 0.25 and a shear stability index (SSI) equal to or greater than 20 percent; and   a. base oil having a viscosity index equal to or greater than 120,   
     wherein the concentration of phosphorus in the lubricant composition is less than 0.08 weight percent and the concentration of sulfur is less than 0.5 weight percent. 
   
   
       13 . A lubricant composition according to  claim 12  wherein the base oil comprises a Group III base stock and/or a Group IV base stock.