Method for preventing exhaust valve seat recession

Abstract

A method for preventing or inhibiting exhaust valve seat recession in a natural gas fueled internal combustion engine is disclosed. The method involves lubricating the engine with a lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity, and (b) a minor amount of a natural gas engine oil additive package, wherein the lubricating oil composition is substantially free of each of any zinc compounds and alkaline earth metal salts of a condensation product of an alkylene polyamine, an aldehyde and a substituted phenol.

1 . A method for preventing or inhibiting exhaust valve seat recession in a natural gas fueled engine, the method comprising lubricating the engine with a lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity; and (b) a minor amount of a natural gas engine oil additive package comprising (i) one or more ashless dispersants, wherein the one or more ashless dispersants includes a bissuccinimide, (ii) a metal-containing detergent mixture comprising a first metal-containing detergent which is an overbased alkaline earth metal sulfonate or phenate detergent having a base number of about 100 to about 450 and a second metal-containing detergent which is an overbased alkaline earth metal sulfonate or phenate detergent having a base number of about 10 to about 50, and (iii) one or more antioxidants, wherein the lubricating oil composition is substantially free of each of any zinc compounds and alkaline earth metal salts of a condensation product of an alkylene polyamine, an aldehyde and a substituted phenol, and further wherein the lubricating oil composition has a sulfated ash content of about 0.1 wt. % to about 1.5 wt. % as determined by ASTM D 874. 
     
     
         2 . The method of  claim 1 , wherein the oil of lubricating viscosity is a natural gas engine lubricating oil. 
     
     
         3 .- 4 . (canceled) 
     
     
         5 . The method of  claim 1 , wherein the bissuccinimide ashless dispersant is derived from one or more polyalkylene succinic anhydrides. 
     
     
         6 . The method of  claim 5 , wherein the polyalkylene group is a polyisobutenyl group having an average molecular weight of from about 700 to about 2300. 
     
     
         7 . The method of  claim 1 , wherein the one or more ashless dispersants is present in an amount of about 1 wt. % to about 8 wt. %, based on the total weight of the lubricating oil composition. 
     
     
         8 .- 10 . (canceled) 
     
     
         11 . The method of  claim 1 , wherein the one or more metal-containing detergents is present in an amount of about 0.5 wt. % to about 8.5 wt. %, based on the total weight of the lubricating oil composition. 
     
     
         12 . The method of  claim 1 , wherein the first metal-containing detergent is present in an amount of about 0.5 wt. % to about 5 wt. % and the second metal-containing detergent is present in an amount of about 0.1 wt. % to about 1 wt. %, based on the total weight of the lubricating oil composition. 
     
     
         13 . The method of  claim 1 , wherein the one or more antioxidants is a hindered phenol compound. 
     
     
         14 . The method of  claim 1 , wherein the one or more antioxidants is present in an amount of about 0.1 wt. % to about 3 wt. %, based on the total weight of the lubricating oil composition. 
     
     
         15 . (canceled) 
     
     
         16 . The method of  claim 1 , wherein the lubricating oil composition has a sulfated ash content of about 0.15 to about 0.5 wt. % as determined by ASTM D 874. 
     
     
         17 . The method of  claim 1 , wherein the lubricating oil composition comprises:
 about 1 wt. % to about 8 wt. % of one or more ashless dispersants,   about 0.5 wt. % to about 8.5 wt. % of one or more metal-containing detergents, and   about 0.1 wt. % to about 3 wt. % of one or more antioxidants, based on the total weight of the lubricating oil composition.   
     
     
         18 . A natural gas engine lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity, (b) one or more ashless dispersants, wherein the one or more ashless dispersants includes a bissuccinimide, (c) a metal-containing detergent mixture comprising a first metal-containing detergent which is an overbased alkaline earth metal sulfonate or phenate detergent having a base number of about 100 to about 450 and a second metal-containing detergent which is an overbased alkaline earth metal sulfonate or phenate detergent having a base number of about 10 to about 50, and (d) one or more antioxidants, wherein the lubricating oil composition is substantially free of each of any zinc compounds and alkaline earth metal salts of a condensation product of an alkylene polyamine, an aldehyde and a substituted phenol, and further wherein the lubricating oil composition has a sulfated ash content of about 0.1 wt. % to about 1.5 wt. % as determined by ASTM D 874. 
     
     
         19 . The natural gas engine lubricating oil composition of  claim 18 , wherein the oil of lubricating viscosity is a natural gas engine lubricating oil. 
     
     
         20 . (canceled) 
     
     
         21 . The natural gas engine lubricating oil composition of  claim 18 , wherein the bissuccinimide ashless dispersant is derived from one or more polyalkylene succinic anhydrides. 
     
     
         22 . The natural gas engine lubricating oil composition of  claim 21 , wherein the polyalkylene group is a polyisobutenyl group having an average molecular weight of from about 700 to about 2300. 
     
     
         23 .- 25 . (canceled) 
     
     
         26 . The natural gas engine lubricating oil composition of  claim 18 , wherein the one or more antioxidants is a hindered phenol compound. 
     
     
         27 . (canceled) 
     
     
         28 . The natural gas engine lubricating oil composition of  claim 18 , having a sulfated ash content of about 0.15 to about 0.5 wt. % as determined by ASTM D 874. 
     
     
         29 . The natural gas engine lubricating oil composition of  claim 18 , comprising:
 about 1 wt. % to about 8 wt. % of one or more ashless dispersants,   about 0.5 wt. % to about 8.5 wt. % of one or more metal-containing detergents, and   about 0.1 wt. % to about 3 wt. % of one or more antioxidants, based on the total weight of the lubricating oil composition.   
     
     
         30 . The natural gas engine lubricating oil composition of  claim 18 , which has an exhaust valve seat recession reducing property greater than that of a corresponding natural gas engine lubricating oil composition in which a zinc compound is present therein. 
     
     
         31 . The method of  claim 1 , wherein the overbased alkaline earth metal sulfonate or phenate detergent having a base number of about 100 to about 450 is a sulfurized calcium phenate and the overbased alkaline earth metal sulfonate or phenate detergent having a base number of about 10 to about 50 is a calcium sulfonate. 
     
     
         32 . The natural gas engine lubricating oil composition of  claim 18 , wherein the overbased alkaline earth metal sulfonate or phenate detergent having a base number of about 100 to about 450 is a sulfurized calcium phenate and the overbased alkaline earth metal sulfonate or phenate detergent having a base number of about 10 to about 50 is a calcium sulfonate.