Lubricating oil composition

Abstract

A lubricating oil composition with enhanced deposit control capability is disclosed for engines operating under sustained high load conditions, such as natural gas engines and low-speed or medium-speed diesel engines. The composition comprises (a) a first base oil component selected from a Group I base stock, a Group II base stock, a Group III base stock, or a combination thereof, each having a kinematic viscosity at 100° C. of from 8.5 to 15 mm 2 /s; and (b) a second base oil component selected from a Group I base stock, a Group II base stock, a Group III base stock, or a combination thereof, each having a kinematic viscosity at 100° C. of from 4.0 to less than 8.5 mm 2 /s; wherein the weight ratio of the first base oil component to the second base oil component is in a range of from 1:10 to 1:1.15.

1 . A natural gas engine lubricating oil composition comprising:
 (a) a first base oil component selected from a Group I base stock, a Group II base stock, a Group III base stock, or a combination thereof, each having a kinematic viscosity at 100° C. of from 8.5 to 15 mm 2 /s; and   (b) a second base oil component selected from a Group I base stock, a Group II base stock, a Group III base stock, or a combination thereof, each having a kinematic viscosity at 100° C. of from 4.0 to less than 8.5 mm 2 /s;   
       wherein the weight ratio of the first base oil component to the second base oil component is in a range of from 1:10 to 1:1.15. 
     
     
         2 . A low-speed or medium-speed diesel engine lubricating oil composition comprising:
 (a) a first base oil component selected from a Group I base stock, a Group II base stock, a Group III base stock, or a combination thereof, each having a kinematic viscosity at 100° C. of from 8.5 to 15 mm 2 /s; and   (b) a second base oil component selected from a Group I base stock, a Group II base stock, a Group III base stock, or a combination thereof, each having a kinematic viscosity at 100° C. of from 4.0 to less than 8.5 mm 2 /s;   
       wherein the weight ratio of the first base oil component to the second base oil component is in a range of from 1:10 to 1:1.15. 
     
     
         3 . The lubricating oil composition of any one of  claim 1  or  2 , wherein the weight ratio of the first base oil component to the second base oil component is in a range of from 1:5 to 1:1.15. 
     
     
         4 . The lubricating oil composition of any one of  claim 1  or  2 , which is a SAE 20, SAE 30, SAE 40, SAE 50 or SAE 60 viscosity grade engine oil. 
     
     
         5 . The lubricating oil composition of any one of  claim 1  or  2 , which is a 15W-x, 20W-x or 25W-x SAE viscosity grade engine oil, wherein x is 30, 40, 50 or 60. 
     
     
         6 . The lubricating oil composition of  claim 2 , wherein the medium-speed diesel engine lubricating oil composition is substantially zinc-free. 
     
     
         7 . The lubricating oil composition of  claim 1 , wherein the lubricating oil composition is used to lubricate a natural gas engine selected from a stationary natural gas engine, a stationary biogas engine, a stationary landfill gas engine, a stationary unconventional natural gas engine, or a dual-fuel engine. 
     
     
         8 . The lubricating oil composition of  claim 2 , wherein the lubricating oil composition is used to lubricate a low-speed diesel engine and the low-speed diesel engine is a marine crosshead diesel engine. 
     
     
         9 . The lubricating oil composition of  claim 2 , wherein the lubricating oil composition is used to lubricate a medium-speed diesel engine selected from a locomotive diesel engine, a marine trunk piston diesel engine or a land-based stationary power diesel engine. 
     
     
         10 . The lubricating oil composition of any one of  claim 1  or  2 , further comprising 1 to 20 wt. %, based on the total weight of the composition, of a polyisobutylene having a kinematic viscosity at 100° C. of from 200 to 5000 mm 2 /s. 
     
     
         11 . The lubricating oil composition of any one of  claim 1  or  2 , further comprising at least one additive selected from an antioxidant, anti-wear agent, metal detergent, dispersant, friction modifier, corrosion inhibitor, demulsifier, viscosity modifier, pour point depressant, foam inhibitor, and mixtures thereof. 
     
     
         12 . A method of controlling deposit formation in a mechanical component of an internal combustion engine selected from a natural gas engine, a low-speed diesel engine or a medium-speed diesel engine, the method comprising operating the internal combustion engine with a lubricating oil composition comprising:
 (a) a first base oil component selected from a Group I base stock, a Group II base stock, a Group III base stock, or a combination thereof, each having a kinematic viscosity at 100° C. of from 8.5 to 15 mm 2 /s; and   (b) a second base oil component selected from a Group I base stock, a Group II base stock, a Group III base stock, or a combination thereof, each having a kinematic viscosity at 100° C. of from 4.0 to less than 8.5 mm 2 /s;   
       wherein the weight ratio of the first base oil component to the second base oil component is in a range of from 1:10 to 1.1:15. 
     
     
         13 . The method of  claim 12 , wherein the mechanical component is a piston, a piston ring, a cylinder liner, a cylinder, a cam, a tappet, a lifter, a gear, a valve, a valve guide, or a bearing including a journal, a roller, a tapered, a needle, or a ball bearing. 
     
     
         14 . The method of  claim 12 , wherein the mechanical component comprises steel. 
     
     
         15 . The method of  claim 12 , wherein the internal combustion engine is operated under a load with a Brake Mean Effective Pressure of greater than 20 bar (2.0 MPa).