Lubricating composition and method of lubricating an internal combustion engine

A method of lubricating a compression ignition internal combustion engine comprising supplying to the engine a low phosphorus lubricant composition comprising:

• a) an oil having a viscosity of 10W-30 or 5W-30;
• b) up to 0.37 weight percent of one or more metal-containing sulfur-free alkyl-phenol based detergents in an amount to deliver at least 0.2 weight percent alkylphenol-containing soap to the composition;
• c) one or more alkaline earth metal sulfonate detergents in an amount to deliver at least 0.8% by weight sulfonate soap to the composition;
• d) 1 wt % to 4 wt % of one or more polyisobutylene succinimide dispersants;
• and
• e) 0.1 wt % to 1.2 wt % of a mixture of dispersant viscosity modifiers, wherein the mixture of dispersant viscosity modifiers comprises at least one low molecular weight dispersant viscosity modifier having a number average molecular weight of less than 10,000, and at least one high molecular weight dispersant viscosity modifier having a number average molecular weight of at least 45,000 up to 1,000,000 with the proviso that the overall number average molecular weight of the mixture of dispersant viscosity modifiers is at least 20,000;
• wherein the lubricating composition contains less than 0.15 weight percent of a sulfur-coupled phenate detergent and wherein the lubricating composition has a viscosity of less than 3.5 cP at 150° C.

A method of reducing adhesive wear in a compression engine lubricated with a low phosphorus lubricant composition, comprising supplying to the engine a lubricant composition comprising:

• a) an oil having a viscosity of 10W-30 or 5W-30;
• b) up to 0.37 weight percent of one or more metal-containing sulfur-free detergents derived from an alkylphenol in an amount to deliver at least 0.2 weight percent alkylphenol-containing soap to the composition;
• c) one or more alkaline earth metal sulfonate detergents in an amount to deliver at least 0.8% by weight sulfonate soap to the composition;
• d) 1 wt % to 4 wt % of one or more polyisobutylene succinimide dispersants;
• and
• e) 0.1 wt % to 1.2 wt % of a mixture of dispersant viscosity modifiers wherein the mixture of dispersant viscosity modifiers comprises at least one low molecular weight dispersant viscosity modifier having a number average molecular weight of less than 10,000 and at least one high molecular weight dispersant viscosity modifier having a number average molecular weight of at least 45,000 up to 1,000,000 with the proviso that the overall number average molecular weight of the mixture of dispersant viscosity modifiers is at least 20,000;
• wherein the lubricating composition contains less than 0.15 weight percent of a sulfur-coupled phenate detergent and wherein the lubricating composition has a viscosity of less than 3.5 cP at 150° C.