Lubricating oil compositions

Abstract

A low ash lubricating oil composition is described. The composition includes major amount of an oil of lubricating viscosity, detergent system, and boron-containing additive in an amount to provide at least 100 ppm of boron to the lubricating oil composition. The detergent system includes one or more magnesium-containing detergent and optionally, one or more calcium-containing detergent. The lubricating oil composition is free of zinc and phosphorus. The total sulfated ash content of the lubricating oil composition is from 0.30 wt. % to 0.80 wt. %. The total base number of the lubricating oil composition is from 4.0 to 9.5 mg KOH/g.

What is claimed is: 
     
         1 . A low ash lubricating oil composition comprising:
 a major amount of an oil of lubricating viscosity;   a detergent system comprising one or more magnesium-containing detergent and optionally, one or more calcium-containing detergent; and   a boron-containing additive in an amount to provide at least 100 ppm of boron to the lubricating oil composition;   wherein the lubricating oil composition is free of zinc and phosphorus; the total sulfated ash content of the lubricating oil composition is from 0.30 wt. % to 0.80 wt. %; and the total base number of the lubricating oil composition is from 4.0 to 9.5 mg KOH/g.   
     
     
         2 . The lubricating oil composition of  claim 1 , wherein the composition contains at least 20 mmol/kg of calcium and/or magnesium detergent. 
     
     
         3 . The lubricating oil composition of  claim 1 , wherein the one or more overbased detergents individually have a total base number of greater than 250 mg KOH/g. 
     
     
         4 . The lubricating oil composition of  claim 1 , wherein the detergent system provides up to 1300 ppm of calcium to the lubricating oil composition. 
     
     
         5 . The lubricating oil composition of  claim 1 , wherein the one or more magnesium-containing detergents is present in an amount to provide 50 to 1000 ppm of magnesium to the lubricating oil composition. 
     
     
         6 . The lubricating oil composition of  claim 1 , further comprising:
 antioxidant, foam inhibitor, viscosity modifier, pour point depressant, dispersant, extreme pressure agent, or metal deactivator.   
     
     
         7 . The lubricating oil composition of  claim 1 , wherein the oil of lubricating viscosity is a Group III base oil. 
     
     
         8 . The lubricating oil composition of  claim 1 , wherein the magnesium-containing detergent is a sulfonate or a salicylate. 
     
     
         9 . The lubricating oil composition of  claim 1 , wherein the calcium-containing detergent is a sulfonate or a salicylate. 
     
     
         10 . A method for reducing corrosion in an engine, the method comprising providing a lubricating oil composition to the engine, wherein the lubricating oil composition comprises:
 a major amount of an oil of lubricating viscosity;   a detergent system comprising one or more calcium overbased detergents and one or more overbased magnesium-containing detergents;   zinc dithiophosphate in an amount to provide a phosphorus content from 0 to 300 ppm to the lubricating oil composition;   boron-containing additive in an amount to provide less than 300 ppm of boron to the lubricating oil composition; and   molybdenum compound in an amount to provide from 50 to 500 ppm of molybdenum to the lubricating oil composition;   wherein the lubricating oil composition has a calcium content of up to about 1300 ppm based on a total weight of the lubricating composition, and where the total sulfated ash content of the lubricating oil composition is from 0.40 wt. % to 0.80 wt. % and the total base number of the lubricating oil composition is from 4.0 to 9.0 mg KOH/g.   
     
     
         11 . The method of  claim 10 , wherein the lubricating oil composition contains at least 20 mmol/kg of calcium and/or magnesium detergent. 
     
     
         12 . The method of  claim 10 , wherein the one or more overbased detergents individually have a total base number of greater than 250 mg KOH/g. 
     
     
         13 . The method of  claim 10 , wherein the detergent system provides up to 1300 ppm of calcium to the lubricating oil composition. 
     
     
         14 . The method of  claim 10 , wherein the one or more magnesium-containing detergents is present in an amount to provide 50 to 1000 ppm of magnesium to the lubricating oil composition. 
     
     
         15 . The method of  claim 10 , wherein the lubricating oil composition further comprises:
 antioxidant, foam inhibitor, viscosity modifier, pour point depressant, dispersant, extreme pressure agent, or metal deactivator.   
     
     
         16 . The method of  claim 10 , wherein the oil of lubricating viscosity is a Group III base oil. 
     
     
         17 . The method of  claim 10 , wherein the magnesium-containing detergent is a sulfonate or a salicylate. 
     
     
         18 . The method of  claim 10 , wherein the calcium-containing detergent is a sulfonate or a salicylate.