Lubricant Compositions

Abstract

Disclosed is a lubricant composition for use in association with a device involving metal-to-metal contact of moving parts, the composition comprising (a) a base stock comprising at least one low viscosity poly-alpha-olefin; (b) a viscosity improver comprising at least one high viscosity poly-alpha-olefin; and (c) a performance additive comprising at least one compound effective to improve at least one property of the lubricant and/or the performance of the equipment in which the lubricant is to be used.

What is claimed is: 
     
         1 . A method for operating Class 8 line haul trucks and vocational vehicles, comprising:
 (a) obtaining an axle fluid, the axle fluid comprising:
 i. basestock comprising at least one PAO having a viscosity in the range of about 4-12 centistokes, 
 ii. a viscosity improver comprising at least one PAO having a viscosity in the range of about 40 to about 1000 centistokes, 
 iii. an ester oil, and 
 iv. optionally, a co-thickener performance additive; and 
   (b) contacting an axle of a Class 8 line haul truck or vocational vehicle with the axle fluid.   
     
     
         2 . The method of  claim 1 , wherein the contacting step comprises contacting moving metal parts. 
     
     
         3 . The method of  claim 2 , wherein a horsepower loss reduction of at least about 3% is achieved. 
     
     
         4 . The method of  claim 2 , wherein a sump temperature reduction of at least about 2% is achieved. 
     
     
         5 . The method of  claim 2 , wherein improved fuel efficiency of the Class 8 line haul truck or vocational vehicle is achieved. 
     
     
         6 . The method of  claim 1 , wherein the axle fluid has a viscosity index in the range of 152-160. 
     
     
         7 . The method of  claim 1 , wherein the axle fluid further comprises, based on the composition, by weight: the basestock (a) in an amount in the range of about 10 to about 90%, the viscosity improver (b) an amount in the range of about 2 to about 70%, the ester oil (c) in an amount in the range of about 2 to about 30%, and performance additive (d) an amount in the range of about 2 to about 30%. 
     
     
         8 . The method of  claim 7 , wherein the axle fluid comprises, based on the composition, by weight: the basestock (a) in an amount in the range of about 15 to about 60%, the viscosity improver (b) in the range of about 5 to about 60%, the ester oil (c) in an amount in the range of about 5 to about 20%, and the performance additive (d) in an amount in the range of about 5 to about 15%. 
     
     
         9 . The method of  claim 1 , wherein said ester oil comprises at least one adipate ester. 
     
     
         10 . The method of  claim 9 , wherein said ester oil consists of one or more adipate esters selected from the group consisting of di-isodecyl adipate and di-tridecyl adipate, and is present in 2-30% by weight, based on the lubricant composition. 
     
     
         11 . The method of  claim 1 , wherein the axle fluid consists essentially of, based on the composition, by weight: the basestock (a) having a viscosity in the range of 6-8 centistokes in an amount in the range of about 15 to about 60%, the viscosity improver (b) having a viscosity in the range of 40-100 centistokes in the range of about 5 to about 60%, the ester oil (c) comprising diisodecyl adipate in an amount in the range of about 5 to about 20%, and the co-thickener (d) comprising a polyisobutylene (PIB), a polymethacrylate (PMA), or an olefin co-polymer (OCP) in an amount in the range of about 5 to about 15%. 
     
     
         12 . The method of  claim 6 , wherein a weight ratio of the at least one PAO having a viscosity in the range of about 4-12 centistokes to the ester oil is in the range of about 0.5:1 to about 12:1. 
     
     
         13 . The method of  claim 6 , wherein the axle fluid comprises:
 (a) a PAO having a viscosity of about 4-12 centistokes in an amount in the range of about 50 to about 60% by weight of the axle fluid,   (b) a PAO having a viscosity of about 100 centistokes in an amount in the range of about 5 to about 40% by weight of the axle fluid, and   (c) di-isodecyl adipate in an amount of about 5% by weight of the axle fluid.