Liquid fuel compositions
Use of a liquid fuel composition in an internal combustion engine, the internal combustion engine containing a lubricating composition for lubricating said internal combustion engine, wherein the liquid fuel composition comprises at least one nitrogen-containing detergent additive, for the purpose of reducing engine wear caused by the presence of soot in the lubricating composition.
1. Method for reducing engine wear in a direct injection gasoline engine caused by the presence of accumulated soot in a lubricating composition used to lubricate the direct injection gasoline engine, wherein the method comprises the steps of:
(i) lubricating the direct injection gasoline engine with a lubricating composition comprising at least one zinc-containing anti-wear additive selected from zinc dialkyl-, diaryl- or alkylaryl-dithiophosphates; and
(ii) fueling the direct injection gasoline engine with a gasoline fuel composition comprising a gasoline base fuel in conjunction with at least one nitrogen-containing detergent additive, and optionally one or more conventional fuel additives, wherein the nitrogen-containing detergent additive is selected from compounds having at least one hydrophobic hydrocarbon radical which is a polyisobutenyl radical having a number-average molecular weight (Mn) of from 85 to 20000 and at least one polar moiety selected from:
(A3) moieties derived from succinic anhydride and having amido and/or imido groups;
wherein the nitrogen-containing detergent additive is present in the gasoline fuel composition at a level from 0.0015 wt % to 0.1 wt %, by weight of the gasoline fuel composition, and wherein the gasoline fuel composition does not contain water;
wherein the amount of accumulated soot present in the lubricating composition is at a level of from 2 wt % to 10 wt %, by weight of the lubricating composition.
2. Method according to claim 1 wherein the nitrogen-containing detergent additive is a polyisobutylene succinimide.
3. Method according to claim 1 wherein the nitrogen-containing detergent additive is present in the fuel composition at a level of from 0.0015 wt % to 0.095 wt %, by weight of the fuel composition.
4. Method according to claim 1 wherein the amount of accumulated soot present in the lubricating composition is from 3.5 to 10 wt %, by weight of the lubricating composition.
5. Method according to claim 1 , wherein the amount of accumulated soot present in the lubricating composition is from 5 to 10 wt %, by weight of the lubricating composition.