Lubricant composition with improved varnish deposit resistance

Abstract

In one embodiment, a lubricating oil with favorable deposit control is disclosed. The lubricating oil comprises, a major amount of base stock selected from the group consisting of Group II, Group III, GTL and any combination thereof, a mannich based dispersant comprising at least 0.1 and less than 2.0 weight percent of the lubricating oil, a demulsifier comprising apolyoxypropylene-polyoxyethylene block copolymer in tricresyl phosphate (TCP) demulsifier and apolyether glycol demulsifier, the demulsifiers comprising at least 0.002 to less than 2.0 weight percent of the lubricating oil, wherein the lubricating oil has a deposit control value less than 60 mg/kg using 504 hour 120° C. Dry TOST sludge test and an ASTM D-1401 emulsion characteristic of less than 60 minutes at 54° C.

What is claimed is: 
     
         1 . A lubricating oil with favorable deposit control and emulsion properties, comprising:
 a) a major amount of base stock selected from the group consisting of Group II, Group III, GTL and any combination thereof;   b) a mannich based dispersant comprising at least 0.1 and less than 2.0 weight percent of the lubricating oil;   c) a demulsifier comprising a first polyoxypropylene-polyoxyethylene block copolymer in TCP, and   d) a polyether glycol demulsifier or a second polyoxypropylene-polyoxyethylene block copolymer demulsifier,   wherein the demulsifiers comprise at least 0.002 to less than 2.0 weight percent of the lubricating oil, and the lubricating oil has a deposit control value less than 60 mg/kg using 504 hour 120° C. Dry TOST sludge test and an ASTM D-1401. emulsion characteristic of less than 60 minutes at 54° C.   
     
     
         2 . The lubricating oil of  claim 1  further comprising at least one additive selected from the group consisting of an antiwear additive, metal passivator, demulsifier, pour point depressant, rust inhibitor, defoamant and any combination thereof. 
     
     
         3 . The lubricating oil of  claim 1  wherein the lubricating oil is a gas turbine oil. 
     
     
         4 . The lubricating oil of  claim 1  wherein the ethylene oxide in the second polyoxypropylene-polyoxyethylene block copolymer comprises less than 25 wt % of the demulsifier, the second polyoxypropylene-polyoxyethylene block copolymer has a molecular weight less than 5000, and the lubricating oil has an ASTM D-1401 emulsion characteristic of less than 3 ml emulsion volume at 30 minutes time at 54° C. 
     
     
         5 . The lubricating oil of  claim 1  wherein the lubricating oil has a ASTM D-4308 electrical conductivity value of greater than 50 pS/m. 
     
     
         6 . The lubricating oil of  claim 1  wherein the lubricating oil has less than 5 PPM calcium and less than 5 PPM zinc. 
     
     
         7 . The lubricating oil of  claim 6  wherein the lubricating oil has a less than 50 PPM phosphorous. 
     
     
         8 . A method for improving the deposit control and emulsion properties of a lubricating oil, comprising:
 a) obtaining a lubricating oil comprising a major amount of base stock selected from the group consisting of Group II, Group III, GTL and any combination thereof, and   b) adding to the lubricating oil a mannich based dispersant comprising at least 0.1 and less than 2.0 weight percent of the lubricating oil, a demulsifier comprising a first polyoxypropylene-polyoxyethylene block copolymer in TCP, and a polyether glycol demulsifier or a second polyoxypropylene-polyoxyethylene block copolymer demulsifier, the demulsifiers comprising at least 0.002 to less than 2.0 weight percent of the lubricating oil,   wherein the lubricating oil has a deposit control value less than 60 mg/kg using 504 hour 120° C. Dry TOST sludge test, and an ASTM D-1401 emulsion characteristic of less than 60 minutes at 54° C.   
     
     
         9 . The method of  claim 8 , wherein the lubricating oil further comprises at least one additive selected from the group consisting of an antiwear additive, metal passivator, demulsifier, pour point depressant, rust inhibitor, defoamant and any combination thereof. 
     
     
         10 . The method of  claim 8  wherein the lubricating oil is a gas turbine oil. 
     
     
         11 . The method of  claim 8  wherein the ethylene oxide in the second polyoxypropylene-polyoxyethylene block copolymer comprises less than 25 wt % of the demulsifier, the second polyonfpropylene-polyoxyethylene block copolymer has a molecular weight less than 5000, and the lubricating oil has an ASTM D-1401. emulsion characteristic of less than 3 ml emulsion volume at 30 minutes time at 54° C. 
     
     
         12 . The method of  claim 8  wherein the lubricating oil has an ASTM D-4308 electrical conductivity value of greater than 50 pS/m. 
     
     
         13 . The method of  claim 8  Wherein the lubricating oil has a less than 5 PPM calcium and less than 5 PPM zinc. 
     
     
         14 . The method of  claim 13  wherein the lubricating oil has a less than 50 PPM phosphorous.