Sulfonate detergent system for improved fuel economy
A composition for lubricating an internal combustion engine includes an oil of lubricating viscosity; a predominantly linear alkylbenzenesulfonate detergent having a metal ratio of at least 8; and a combination of hindered phenolic ester antioxidant and aromatic amine antioxidant. The amount of any phenate detergent is less than 15% by weight of the total amount of detergents.
1. A composition suitable for lubricating an internal combustion engine, comprising:
(a) an oil of lubricating viscosity;
(b) an overbased detergent, wherein the detergent is exclusively or predominantly a linear alkylbenzenesulfonate detergent having a metal ratio of at least about 8, wherein in said composition the amount of phenate detergent is less than about 15% by weight of the total amount of detergents
(c) a combination of antioxidants comprising
(i) about 0.1 to about 2 weight percent hindered phenolic ester antioxidant and
(ii) about 0.2 to about 2 weight percent aromatic amine antioxidant; and
(d) at least one further component selected from the group consisting of dispersants, zinc dialkyldithiophosphates, and friction modifiers.
2. The composition of claim 1 wherein the detergent is exclusively or predominantly a calcium overbased synthetic linear alkylbenzenesulfonate detergent, the alkylbenzene group in said detergent having a number average molecular weight of about 320 to about 700.
3. The composition of claim 2 wherein the composition contains less than about 500 parts per million by weight of metals other than calcium or zinc.
4. The composition of claim 1 further comprising at least one salicylate detergent, saligenin detergent, or salixarate detergent.
5. The composition of claim 1 wherein the amount of any detergent other than the alkylbenzenesulfonate detergent is less than about 15% of the amount of the total amount of detergents.
6. The composition of claim 1 wherein the amount of any phenate detergent is less than about 1% by weight of the total amount of detergents.
7. The composition of claim 1 wherein the composition comprises a zinc dialkyldithiophosphate wherein said alkyl groups are predominantly secondary, in an amount to deliver about 0.025 to about 0.1 weight percent phosphorus to the composition.
8. The composition of claim 1 wherein the antioxidant component (c) further comprises about 0.1 to about 1 weight percent of a sulfurized olefin.
9. The composition of claim 8 wherein the sulfurized olefin is sulfurized 4-carbobutoxy cyclohexene.
10. A composition prepared by admixing the components of claim 1 .
11. A method for lubricating an internal combustion engine, comprising supplying thereto the composition of claim 1 .
12. A composition suitable for lubricating an internal combustion engine, comprising:
(a) an oil of lubricating viscosity;
(b) an overbased detergent, wherein the detergent is exclusively or predominantly a synthetic linear alkylbenzenesulfonate detergent having a metal ratio of at least about 8 and the alkylbenzene group therein having a number average molecular weight of about 320 to about 700, wherein in said composition the amount of phenate detergent is less than about 1% by weight of the total amount of detergents and the total amount of detergents other than the alkylbenzenesulfonate is less than about 15% by weight of the total amount of detergents;
(c) a combination of antioxidants comprising
(i) about 0.1 to about 2 weight percent hindered phenolic ester antioxidant,
(ii) about 0.2 to about 2 weight percent aromatic amine antioxidant, and
(iii) about 0.1 to about 1 weight percent of a sulfurized olefin antioxidant; and
(d) a zinc dialkyldithiophosphate wherein said alkyl groups are predominantly secondary, in an amount to deliver about 0.025 to about 0.1 weight percent phosphorus to the composition;
wherein the composition contains less than about 300 parts per million by weight of metals other than calcium or zinc.
13. A concentrate comprising
(a) a concentrate-forming amount of an oil of lubricating viscosity;
(b) an overbased detergent, wherein the detergent is exclusively or predominantly a linear alkylbenzenesulfonate detergent having a metal ratio of about at least about 8 and the alkylbenzene group therein having a number average molecular weight of about 320 to about 700, wherein in said composition the amount of phenate detergent is less than about 15% by weight of the total amount of detergents;
(c) a combination of antioxidants comprising
(i) hindered phenolic ester antioxidant and
(ii) aromatic amine antioxidant; and
(d) at least one further component selected from the group consisting of dispersants, zinc dialkyldithiophosphates, and friction modifiers.