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, 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. 
   
   
       2 . The method of  claim 1 , wherein the oil of lubricating viscosity is a natural gas engine lubricating oil. 
   
   
       3 . The method of  claim 1 , wherein the natural gas engine oil additive package includes (i) one or more ashless dispersants, (ii) one or more metal-containing detergents, and (iii) one or more antioxidants. 
   
   
       4 . The method of  claim 3 , wherein the one or more ashless dispersants is a bissuccinimide. 
   
   
       5 . The method of  claim 4 , 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 3 , 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 . The method of  claim 3 , wherein the one or more metal-containing detergents is an overbased alkaline earth metal salt detergent having a base number (BN) of about 10 to about 450. 
   
   
       9 . The method of  claim 3 , wherein the one or more metal-containing detergents comprises two metal-containing detergents. 
   
   
       10 . The method of  claim 9 , wherein the two metal-containing detergents comprise a first metal-containing detergent which is an overbased alkaline earth metal phenate detergent having a BN of about 100 to about 450 and a second metal-containing detergent which is an overbased alkaline earth metal sulfonate detergent having a BN of about 10 to about 50. 
   
   
       11 . The method of  claim 3 , 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 10 , 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 3 , wherein the one or more antioxidants is a hindered phenol compound. 
   
   
       14 . The method of  claim 3 , 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 . The method of  claim 1 , 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. 
   
   
       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, (c) one or more metal-containing detergents, 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. 
   
   
       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 . The natural gas engine lubricating oil composition of  claim 18 , wherein the one or more ashless dispersants is a bissuccinimide. 
   
   
       21 . The natural gas engine lubricating oil composition of  claim 20 , 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 . The natural gas engine lubricating oil composition of  claim 18 , wherein the one or more metal-containing detergents is an overbased alkaline earth metal salt detergent having a BN of about 10 to about 450. 
   
   
       24 . The natural gas engine lubricating oil composition of  claim 23 , wherein the one or more metal-containing detergents comprises two metal-containing detergents. 
   
   
       25 . The natural gas engine lubricating oil composition of  claim 24 , wherein the two metal-containing detergents comprise a first metal-containing detergent which is an overbased alkaline earth metal phenate detergent having a BN of about 100 to about 450 and a second metal-containing detergent which is an overbased alkaline earth metal sulfonate detergent having a BN of about 10 to about 50. 
   
   
       26 . The natural gas engine lubricating oil composition of  claim 18 , wherein the one or more antioxidants is a hindered phenol compound. 
   
   
       27 . The natural gas engine lubricating oil composition of  claim 18 , having a sulfated ash content of about 0.1 wt. % to about 1.5 wt. % as determined by ASTM D 874. 
   
   
       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.