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 a polyol ester and a poly oxyakylene, 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 using 504 hour 120° C. Dry TOST sludge test. In a second embodiment a method of deposit control is disclosed. In a third embodiment a method of formulating an oil to improve deposit control and emulsion properties is disclosed.

1 . A lubricating oil with favorable deposit varnish 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 polyol ester and a poly oxyakylene alcohol, the demulsifiers comprising at least 0.002 to less than 2.0 weight percent of the lubricating oil; and   d) the lubricating oil has a deposit control value less than 60 using 504 hour 120° C. Dry TOST sludge test.   
   
   
       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 polyol ester in the demulsifier comprises less than 25 wt % of the demulsifier and has a molecular weight less than 5000 and the lubricating oil has a ASTM D-1401 emulsion characteristic of less than 60 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. 
   
   
       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 of improving the deposit control comprising:
 a) obtaining a lubricating oil with favorable deposit varnish properties, comprising 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 a polyol ester and a poly oxyakylene, 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 using 504 hour 120° C. Dry TOST sludge test; and   b) lubricating with the lubricating oil.   
   
   
       9 . The lubricating oil of  claim 8  further comprising at least one additive selected form the group consisting of an antiwear additive, metal passivator, demulsifier, pour point depressant, rust inhibitor, defoamant and any combination thereof. 
   
   
       10 . The lubricating oil of  claim 8  wherein the lubricating oil is a gas turbine oil. 
   
   
       11 . The lubricating oil of  claim 8  wherein the polyol ester in the demulsifier comprises less than 25 wt % of the demulsifier and has a molecular weight less than 5000 and the lubricating oil has a ASTM D-1401 emulsion characteristic of less than 60 at 54° C. 
   
   
       12 . The lubricating oil of  claim 8  wherein the lubricating oil has a ASTM D-4308 electrical conductivity value of greater than 50. 
   
   
       13 . The lubricating oil of  claim 8  wherein the lubricating oil has a less than 5 PPM calcium and less than 5 PPM zinc. 
   
   
       14 . The lubricating oil of  claim 13  wherein the lubricating oil has a less than 50 PPM phosphorous. 
   
   
       15 . A method of blending a oil to provide improved deposit control and favorable emulsion properties comprising:
 a) obtaining 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 a polyol ester and a poly oxyakylene, the demulsifiers comprising at least 0.002 to less than 2.0 weight percent of the lubricating oil; and   b) formulating the base stocks, demulsifiers and dispersants to have a deposit control value less than 60 using 504 hour 120° C. Dry TOST sludge test.   
   
   
       16 . The lubricating oil of  claim 15  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. 
   
   
       17 . The method of  claim 15  wherein the polyol ester in the demulsifier comprises less than 25 wt % of the demulsifier and has a molecular weight less than 5000 and the lubricating oil has a ASTM D-1401 emulsion characteristic of less than 60 at 54° C. 
   
   
       18 . The lubricating oil of  claim 1  further comprising a propylene oxide block copolymer. 
   
   
       19 . The lubricating oil of  claim 8  further comprising a propylene oxide block copolymer. 
   
   
       20 . The lubricating oil of  claim 15  further comprising a propylene oxide block copolymer.