Use of a fuel composition comprising a major amount of a fuel suitable for use in a compression-ignition engine, which fuel comprises one or more hydrocarbon components boiling within the diesel boiling range, at least one of which hydrocarbon components has been treated with a metal adsorbing or absorbing material in a different physical phase from the hydrocarbon component(s), preferably to reduce the level of at least one metal, more preferably the level of at least one heavier metal, most preferably the level of copper and/or iron and/or zinc, in said at least one hydrocarbon component, said treatment including physical separation of the hydrocarbon component from the metal adsorbing or absorbing phase, for the purpose of reducing subsequent formation of deposits, preferably combustion related deposits, during engine operation in a compression- ignition engine into which the fuel composition is introduced and/or of removing from the engine previously incurred deposits. Preferably the level of deposits in the engine after engine operation with said fuel composition in the engine is lower than the level of deposits in the engine after engine operation with an alternative fuel composition in the engine, said alternative fuel composition having essentially the same characteristics as said fuel composition but the hydrocarbon components of which have not been treated with said metal adsorbing or absorbing material.