Lubricating oils with enhanced piston deposit control capability

Abstract

The lubricant composition of the present disclosure comprises a major amount of a base oil and a minor amount of an additive composition comprising an overbased detergent and a low-base detergent, wherein the lubricant composition has a salt to metal ratio ranging from about 3.0 to about 8.0.

1 . A lubricant composition comprising:
 a major amount of a base oil; and   a minor amount of an additive composition comprising an overbased detergent and a low-base detergent,   wherein the lubricant composition has a salt to metal ratio ranging from about 3.0 to about 8.0.   
     
     
         2 . The lubricant composition of  claim 1 , wherein the overbased detergent and low-base detergent are selected from the group consisting of sulfonates, phenates, sulfurized phenates, carboxylates, salicylates, thiophosphonates, naphthenates of a metal, and combinations thereof. 
     
     
         3 . The lubricant composition of  claim 1 , wherein the overbased detergent is present in an amount ranging from about 0.5 wt. % to about 3.5 wt. %, relative to the total weight of the composition. 
     
     
         4 . The lubricant composition of  claim 1 , wherein the overbased detergent has a total base number greater than about 150. 
     
     
         5 . The lubricant composition of  claim 4 , wherein the overbased detergent has a total base number greater than about 250. 
     
     
         6 . The lubricant composition of  claim 1 , wherein the overbased detergent has a metal content ranging from about 0.05 wt. % to about 0.7 wt. %. 
     
     
         7 . The lubricant composition of  claim 6 , wherein the overbased detergent has a metal content ranging from about 0.1 wt. % to about 0.5 wt. %. 
     
     
         8 . The lubricant composition of  claim 1 , wherein the weight ratio of the low-base detergent to the overbased detergent ranges from about 0.1 to about 7. 
     
     
         9 . The lubricant composition of  claim 1 , wherein the low-base detergent is present in an amount ranging from about 0.1 wt. % to about 3.5 wt. % relative to the total weight of the composition. 
     
     
         10 . The lubricant composition of  claim 1 , wherein the low-base detergent has a total base number of about 150 or less. 
     
     
         11 . The lubricant composition of  claim 10 , wherein the low-base detergent has a total base number less than about 80. 
     
     
         12 . The lubricant composition of  claim 1 , wherein the low-base detergent has a metal content ranging from about 0.005 wt. % to about 0.175 wt. %. 
     
     
         13 . The lubricant composition of  claim 6 , wherein the low-base detergent has a metal content ranging from about 0.025 wt. % to about 0.15 wt. %. 
     
     
         14 . The lubricant composition of  claim 1 , wherein the lubricant composition has a salt to metal ratio ranging from about 3.5 to about 7.5. 
     
     
         15 . The lubricant composition of  claim 1 , wherein the lubricant composition has a salt to metal ratio ranging from about 4.0 to about 6.5. 
     
     
         16 . The lubricant composition of  claim 1 , further comprising at least one additive selected from the group consisting of dispersants, anti-wears, antioxidants, friction modifiers, anti-foamers, diluents, pour-point depressants, and viscosity index improvers. 
     
     
         17 . A method of improving piston cleanliness comprising:
 providing to at least one piston a lubricant composition comprising a major amount of a base oil; and a minor amount of an additive composition comprising an overbased detergent and a low-base detergent,   wherein the lubricant composition has a salt to metal ratio ranging from about 3.0 to about 8.0.   
     
     
         18 . A method of passing a Sequence IIIG test in a combustion system comprising:
 providing to the combustion system a lubricant composition comprising a major amount of a base oil; and a minor amount of an additive composition comprising an overbased detergent and a low-base detergent,   wherein the lubricant composition has a salt to metal ratio ranging from about 3.0 to about 8.0.   
     
     
         19 . A method of passing a Sequence IIIG test in a combustion system comprising:
 providing to the combustion system a lubricant composition comprising a major amount of a base oil; and a minor amount of an additive composition comprising an overbased detergent and a low-base detergent,   wherein the lubricant composition has a salt to metal ratio ranging from about 3.0 to about 8.0.   
     
     
         20 . The method of  claim 19 , wherein the machine is selected from the group consisting of spark ignition and compression-ignition internal combustion engines.