Method of lubricating an internal combustion engine

Abstract

The invention provides a method of lubricating a compression-ignition internal combustion engine with a maximum laden mass over 2,700 kg comprising supplying to the engine a lubricating composition comprising: an oil of lubricating viscosity, a 300 TBN or higher alkaline earth metal sulphonate detergent having a metal ratio of 10 to 40, 0.1 wt % to 4 wt % of a borated polyisobutylene succinimide dispersant, wherein the polyisobutylene from which the borated polyisobutylene succinimide is derived has a number average molecular weight of 550 to 1150, and 0.1 wt % to 6 wt % of a polyisobutylene succinimide, wherein the polyisobutylene from which polyisobutylene succinimide is derived has a number average molecular weight of 1550 to 2500, 0 wt % to 0.2 wt % of a phenolic based detergent, wherein the total amount of soap delivered by the alkaline earth metal sulphonate (typically calcium sulphonate) is 0.4 to 1 wt % of the lubricating composition, and wherein the lubricating composition has a sulphated ash content of not more than 1.5 wt %.

What is claimed is: 
     
         1 . A method of lubricating a compression-ignition internal combustion engine with a maximum laden mass over 2,700 kg comprising supplying to the engine a lubricating composition comprising:
 an oil of lubricating viscosity,   a 300 TBN or higher alkaline earth metal sulphonate detergent having a metal ratio of 10 to 40,   0.1 wt % to 4 wt % of a borated polyisobutylene succinimide dispersant, wherein the polyisobutylene from which the borated polyisobutylene succinimide is derived has a number average molecular weight of 550 to 1150, and   0.1 wt % to 6 wt % of a polyisobutylene succinimide, wherein the polyisobutylene from which polyisobutylene succinimide is derived has a number average molecular weight of 1550 to 2500,   0 wt % to 0.2 wt % of a phenolic based detergent,   
       the total amount of soap delivered by the 300 TBN or higher alkaline earth metal sulphonate is 0.4 to 1 wt % of the lubricating composition, and 
       the lubricating composition has a sulphated ash content of not more than 1.5 wt %. 
     
     
         2 . The method of  claim 1 , wherein the lubricating composition has (i) a sulphur content of 0.5 wt % or less, (ii) a phosphorus content of 0.1 wt % or less, and (iii) a sulphated ash content of 0.5 wt % to 1.5 wt %. 
     
     
         3 . The method of  claim 1 , wherein the lubricating composition has at least one of (i) a sulphur content of 0.2 wt % to 0.4 wt %, (ii) a phosphorus content of 0.08 wt % to 0.15 wt %, and (iii) a sulphated ash content of 0.5 wt % to 1.5 wt %. 
     
     
         4 . The method of  claim 2 , wherein the lubricating composition has a sulphated ash content of 0.5 wt % to 1.2 wt %. 
     
     
         5 . The method of  claim 1 , wherein the lubricating composition has a total base number (TBN) content of at least 5 mg KOH/g. 
     
     
         6 . The method of  claim 5 , wherein the lubricating composition has a total base number (TBN) content of 7 to 10 mg KOH/g. 
     
     
         7 . The method of  claim 1 , wherein the 300 TBN or higher alkaline earth metal sulphonate detergent is a calcium sulphonate detergent and the total amount of soap delivered by the calcium sulphonate detergent is 0.5 to 0.8 wt % of the lubricating composition. 
     
     
         8 . The method of  claim 1 , wherein the lubricating composition further comprises a 80 TBN or lower alkaline earth metal sulphonate detergent having a metal ratio of 1 to 5. 
     
     
         9 . The method of  claim 8 , wherein the ratio of the 300 TBN or higher alkaline earth metal sulphonate detergent to the 80 TBN or lower alkaline earth metal sulphonate detergent is 80:20 to 20:80. 
     
     
         10 . The method of  claim 1 , wherein the metal ratio of the 300 TBN or higher alkaline earth metal sulphonate detergent is 20 to 30. 
     
     
         11 . The method of  claim 1 , wherein the 300 TBN or higher alkaline earth metal sulphonate detergent has a TBN of 350 to 500. 
     
     
         12 . The method of  claim 8 , wherein the 80 TBN or lower alkaline earth metal sulphonate detergent has a metal ratio of 1 to 3. 
     
     
         13 . The method of  claim 8 , wherein the 80 TBN or lower alkaline earth metal sulphonate detergent is a calcium sulphonate detergent having a TBN of 1 to 80. 
     
     
         14 . The method of  claim 1 , wherein the lubricating composition comprises up to 0.1 wt % of a phenolic based detergent. 
     
     
         15 . The method of  claim 1 , wherein the lubricating composition comprises 0 wt % of a phenolic based detergent. 
     
     
         16 . The method of  claim 1 , wherein the lubricating composition further comprises a dispersant viscosity modifier. 
     
     
         17 . The method of  claim 16 , wherein the dispersant viscosity modifier is present at 0.01 wt % to 3 wt %. 
     
     
         18 . The method of  claim 17 , wherein the dispersant viscosity modifier is an olefin copolymer further functionalised with a dispersant amine group. 
     
     
         19 . The method of  claim 18 , wherein the olefin copolymer is an ethylene-propylene copolymer. 
     
     
         20 . The method of  claim 18 , wherein the olefin copolymer has a number average molecular weight of 5000 to 100,000, or 7500 to 60,000, or 8000 to 45,000. 
     
     
         21 . The method of  claim 16 , wherein the dispersant amine group is derived from reacting the olefin copolymer with an acylating agent and an aromatic amine having a primary or secondary amino group. 
     
     
         22 . The method of  claim 21 , wherein the aromatic amine comprises 4-aminodiphenylamine, aldehyde (typically formaldehyde) coupled 4-aminodiphenylamine, nitro-aniline, disperse orange-3 (D03), or mixtures thereof. 
     
     
         23 . The method of  claim 1 , wherein the lubricating composition further comprises an antioxidant, wherein the antioxidant comprises a phenolic or an aminic antioxidant or mixtures thereof, and wherein the antioxidant is present at 0.1 wt % to 3 wt %. 
     
     
         24 . The method of  claim 1 , wherein the lubricating composition further comprises a phosphorus-containing antiwear agent, typically zinc dialkyldithiophosphate. 
     
     
         25 . The method of  claim 1 , wherein the polyisobutylene succinimide is present at 2.5 wt % to 6 wt %. 
     
     
         26 . The method of  claim 1 , wherein the polyisobutylene succinimide and the borated polyisobutylene succinimide have a carbonyl to nitrogen ratio of 1:1 to 1:5. 
     
     
         27 . The method of  claim 1 , wherein the borated polyisobutylene succinimide is present at 0.1 to 2 wt %, or 0.2 wt % to 1 wt %. 
     
     
         28 . The method of  claim 1 , wherein the polyisobutylene succinimide is present in an amount greater than the borated polyisobutylene succinimide. 
     
     
         29 . The method of  claim 28 , wherein the borated polyisobutylene succinimide contributes 5 wt % to 25 wt % of dispersant present; and polyisobutylene succinimide contributes 75 wt % to 95 wt % of dispersant present.