Abstract: The invention provides a method for the production of a diesel fuel composition, said method using Gas-to-Liquid (GTL) diesel fuel as a blend component together with at least a crude oil derived diesel fuel, said method producing a diesel fuel composition which, when combusted in an engine, has reduced NOx and soot emissions. The invention further provides a diesel fuel composition and a method of reducing NOx and soot emissions from a Cl engine.

Abstract: The invention provides a compression ignition engine fuel derived from a Fischer-Tropsch process, which fuel has a generally increasing iso:n paraffins ratio with increasing paraffin carbon number at least between C9 to C18, less than 0.05% m/m sulphur, and less than 10% by mass aromatics. The fuel may have on average more than 0.9 alkyl branches per paraffinic molecule as measured by H+ NMR analysis. The invention also provides a method for operating a compression ignition engine to produce low particulates emissions, which method comprises combusting the fuel with oxygen or an oxygen containing gas in the engine. Yet further the invention provides a method of improving the conversion efficiency of oxidation catalysts used in conjunction with compression ignition engines, said method including combusting the fuel in the compression ignition engine in the presence of said oxidation catalysts and in oxygen or an oxygen containing gas.