Lubricating oil composition

Abstract

A molybdenum-free lubricating oil composition exhibiting improved fuel economy and fuel economy retention properties, which comprises: (a) a major amount of base stock selected from the group consisting of one or more Group IV or Group V oils and mixtures thereof, and mixtures containing one or more Group III oils and at least one Group IV and/or Group V oils, the base stock having a NOACK volatility of 12% or less; and; (b) at least one calcium detergent; and (c) 0.2 to 2.0 wt. % of an organic friction modifier, wherein the composition has a NOACK volatility of about 12 wt. % or less and contains from about 0.058 to 0.58 wt. % calcium from the calcium detergent.

What is claimed is:  
     
         1 . A lubricating oil composition for internal combustion engines which exhibits improved fuel economy and fuel economy retention properties, is free of molybdenum additives, has a NOACK volatility of 12 wt. % or less and which comprises: 
 (a) a major amount of base stock selected from the group consisting of one or more Group IV or Group V oils and mixtures thereof, and mixtures containing one or more Group III oils and at least one Group IV and/or Group V oils, the base stock having a NOACK volatility of 12% or less; and    (b) a calcium detergent present in such amounts so as to provide from about 0.058 to about 0.58 wt. % calcium in the composition; and    (c) from about 0.02 to about 2.0 wt. % of an oil soluble organic friction modifier.    
     
     
         2 . The composition of  claim 1 , wherein the base stock comprises a poly-α-olefin synthetic base stock.  
     
     
         3 . The composition of  claim 1 , wherein said NOACK volatility of said base stock is 10% or less.  
     
     
         4 . The composition of  claim 1 , wherein said NOACK volatility of said base stock is 8% or less.  
     
     
         5 . The composition of  claim 1 , wherein the composition further comprises a zinc dialkyl dithiophosphate present in such amount to provide up to 0.1 wt. % phosphorus in the composition.  
     
     
         6 . The composition of  claim 5 , wherein the zinc dialkyldithiophosphate has at least 50 wt. % secondary alkyl groups.  
     
     
         7 . The composition of  claim 1 , wherein the calcium detergent is overbased.  
     
     
         8 . The composition of  claim 7 , wherein the calcium detergent is a sulfonate.  
     
     
         9 . The composition of  claim 1 , wherein the composition further comprises one or more of lubricating oil additives selected from the group consisting of ashless dispersants, other metal detergents, corrosion inhibitors, supplemental antioxidants, pour point depressants, anti-foaming agents, supplemental antiwear agents, other friction modifiers and viscosity modifiers present in such amounts so as to provide their normal attendant functions.  
     
     
         10 . The composition of  claim 1 , wherein said base stock has a kinematic viscosity index of of from about 3 to about 12 mm 2 /s.  
     
     
         11 . The composition of  claim 10 , wherein said base stock has a kinematic viscosity of from about 4 to about 10 mm 2 /s.  
     
     
         12 . The composition of  claim 1 , wherein said base stock has a viscosity of at least 120.  
     
     
         13 . The composition of  claim 12 , wherein said base stock has a viscosity of at least 130.