Lubricating oil compositions

Abstract

A method for preventing or inhibiting exhaust valve seat recession in a natural gas fueled engine, the method comprising lubricating the engine with a natural gas engine lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity, and (b) an alkali metal-containing detergent, wherein the natural gas engine lubricating oil composition is substantially free of each of any alkaline earth metal-containing detergents and lithium-containing detergents is disclosed.

1 . A natural gas engine lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity; and (b) about 0.5 to about 8.0 wt. %, based on the total weight of the natural gas engine lubricating oil composition, of a low or medium overbased alkali metal-containing detergent having a BN from about 1 to about 200, wherein the low or medium overbased alkali metal-containing detergent is a potassium alkylhydroxybenzoate deterrent and wherein the natural gas engine lubricating oil composition is substantially free of each of any alkaline earth metal-containing detergents and lithium-containing detergents, and further wherein the natural gas engine lubricating oil composition has a sulfated ash content of no more than about 0.95 wt. % as determined by ASTM D 874. 
     
     
         2 . The natural gas engine lubricating oil composition of  claim 1 , further including a sodium-containing detergent. 
     
     
         3 . The natural gas engine lubricating oil composition of  claim 2 , wherein the sodium-containing detergent is a sodium petroleum sulfonate detergent. 
     
     
         4 . The natural gas engine lubricating oil composition of  claim 3 , wherein the sodium petroleum sulfonate detergent is a neutral sodium petroleum sulfonate detergent. 
     
     
         5 .- 7 . (canceled) 
     
     
         8 . The natural gas engine lubricating oil composition of  claim 1 , further comprising (c) one or more dispersants; (d) one or more antioxidants; and (e) one or more anti-wear agents. 
     
     
         9 . The natural gas engine lubricating oil composition of  claim 8 , wherein the one or more ashless dispersants is a bisuccinimide. 
     
     
         10 . The natural gas engine lubricating oil composition of  claim 9 , wherein the bisuccinimide ashless dispersant is derived from one or more polyalkylene succinic anhydrides. 
     
     
         11 . The natural gas engine lubricating oil composition of  claim 10 , wherein the polyalkylene group is a polyisobutenyl group having an average molecular weight of from about 700 to about 2300. 
     
     
         12 . The natural gas engine lubricating oil composition of  claim 8 , wherein the one or more ashless dispersants is present in an amount of about 1.0 wt. % to about 8.0 wt. %, based on the total weight of the lubricating oil composition. 
     
     
         13 . The natural gas engine lubricating oil composition of  claim 8 , wherein the one or more antioxidants is a hindered phenol compound. 
     
     
         14 . The natural gas engine lubricating oil composition of  claim 8 , wherein the one or more antioxidants is present in an amount of about 0.1 wt. % to about 3.0 wt. %, based on the total weight of the lubricating oil composition. 
     
     
         15 . The natural gas engine lubricating oil composition of  claim 8 , wherein the one or more anti-wear agents is a zinc di-alkyl di-thiophosphate. 
     
     
         16 . The natural gas engine lubricating oil composition of  claim 8 , wherein the one or more anti-wear agents is present in an amount of about 0.1 wt. % to about 4.0 wt. %, based on the total weight of the lubricating oil composition. 
     
     
         17 . The natural gas engine lubricating oil composition of  claim 1 , further comprising:
 about 1.0 to about 8.0 wt. % of one or more ashless dispersants,   about 0.1 to about 3.0 wt. % of one or more antioxidants, and   about 0.1 to about 4.0 wt. % of one or more anti-wear agents, based on the total weight of the lubricating oil composition.   
     
     
         18 . The natural gas engine lubricating oil composition of  claim 1 ,
 wherein the natural gas engine lubricating oil composition has a sulfated ash content of about 0.1 wt. % to about 0.95 wt. % as determined by ASTM D 874.   
     
     
         19 . The natural gas engine lubricating oil composition of  claim 17 , wherein the natural gas engine lubricating oil composition has a sulfated ash content of about 0.1 wt. % to about 0.95 wt. % as determined by ASTM D 874. 
     
     
         20 - 32 . (canceled)