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 sulphonates (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 calcium 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;   an 80 TBN or lower calcium sulphonate detergent having a metal ratio of 1 to 5;   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; and   0.1 to 1.0 wt % of a dispersant viscosity modifier;   wherein,   the total soap delivered to the lubricating composition by the calcium sulphonate detergents is 0.4 wt % to 1.5 wt %, the lubricating composition has a sulphated ash content of not more than 1.5 wt %, a sulphur content of 0.5 wt % or less, a phosphorus content of 0.1 wt % or less, and the lubricating composition has 0 wt % of a phenolic based detergent.   
     
     
         2 . 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 %, and (ii) a phosphorus content of 0.08 wt % to 0.15 wt %. 
     
     
         3 . The method of  claim 1 , wherein the lubricating composition has a total base number (TBN) content of at least 5 mg KOH/g. 
     
     
         4 . The method of  claim 1 , wherein the lubricating composition has a total base number (TBN) content of 7 to 10 mg KOH/g. 
     
     
         5 . The method of  claim 1 , wherein the 300 TBN or higher calcium sulphonate detergent has a TBN of 350 to 500. 
     
     
         6 . The method of  claim 1 , wherein the 80 TBN or lower calcium sulphonate has a TBN of 1 to 80. 
     
     
         7 . The method of  claim 1 , wherein the dispersant viscosity modifier is an olefin copolymer further functionalised with a dispersant amine group. 
     
     
         8 . The method of  claim 7 , wherein the olefin copolymer is an ethylene-propylene copolymer. 
     
     
         9 . The method of  claim 7 , wherein the olefin copolymer has a number average molecular weight of 5000 to 100,000. 
     
     
         10 . The method of  claim 7 , 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. 
     
     
         11 . The method of  claim 10 , wherein the aromatic amine comprises 4 aminodiphenylamine, aldehyde coupled 4 aminodiphenylamine, nitro-aniline, disperse orange-3 (DO3), or mixtures thereof. 
     
     
         12 . 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 %. 
     
     
         13 . The method of  claim 1 , wherein the lubricating composition further comprises a phosphorus-containing antiwear agent. 
     
     
         14 . The method of  claim 1 , wherein the polyisobutylene succinimide is present at 2.5 wt % to 6 wt %. 
     
     
         15 . 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. 
     
     
         16 . The method of  claim 1 , wherein the borated polyisobutylene succinimide is present at 0.1 to 2 wt %. 
     
     
         17 . The method of  claim 1 , wherein the polyisobutylene succinimide is present in an amount greater than the borated polyisobutylene succinimide. 
     
     
         18 . The method of  claim 1 , wherein the borated polyisobutylene succinimide contributes 5 wt % to 25 wt % of dispersant present in the lubricating composition and the polyisobutylene succinimide contributes 75 wt % to 95 wt % of dispersant present in the lubricating composition. 
     
     
         19 . The method of  claim 1 , wherein the ratio of the 300 TBN calcium sulphonate detergent to the 80 TBN or lower calcium sulphonate detergent is from 80:20 to 20:80.