Improvements relating to fuel economy

Abstract

The use of a viscosity increasing component in a diesel fuel composition is described for the purpose of improving the fuel economy of an engine or of a vehicle powered by such an engine. The viscosity increasing component is a viscosity index (VI) improving additive, such as a polystyrene-polyisoprene stellate copolymer. The diesel fuel may comprise a biofuel. Methods of using a viscosity increasing component for purposes of improving fuel economy, and methods of operating a compression ignition engine are also described,

Description

technical field [0001] The present invention relates to methods of improving diesel fuel economy in compression ignition (diesel) engines; and in particular the use of viscosity enhancing components in diesel fuel compositions to improve fuel economy. Background technique [0002] Currently, emission regulations such as those in the United States and Europe set strict limits on acceptable levels of polluting gases that are tolerated in the exhaust emissions of compression ignition engines. [0003] A common approach taken by engine and fuel manufacturers to improve the combustion process and reduce the generation of unwanted exhaust emissions is to utilize some form of "advanced combustion". Advanced combustion is a catch-all term that includes many different fuel modes, and it typically includes one or more of the following features: fuel injection well ahead of top dead center (TDC); multiple fuel injections; extensive exhaust gas recirculation (EGR) ; and high injection ...

AI Technical Summary

Problems solved by technology

[0009] Furthermore, since the amount of fuel injected into a motor vehicle's engine is primarily governed by volume, a reduction in fuel density results in a reduction in the amount of combustible fuel in the engine cylinders and a consequent reduction in the effective amount of energy that can be converted

This drives engine emissions further in the direction of low NOx and high PM, but at the expense of engine efficiency and increased fuel consumption

Even though this may have a small benefit in NOx emissions, it has been realized that this setup does not provide the optimum balance between fuel economy and exhaust emissions that motor vehicle manufacturers want

[0010] Given the above operating procedures and issues, it is difficult to achieve an optimal balance between fuel economy and exhaust emissions using only standard refinery fuels

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