Abstract: The diesel purifier produces a fuel of high purity that meets the full ignition requirements at the combustion chamber of the engine. The purifier comprises a purification chamber encapsulated by an external body of the unit wherein, the purification chamber has a barrier with conical and cylindrical parts surrounded by a filter, such that fuel flows from the unit inlet through a pipe to the conical part, further wherein the upper part of the unit has a relief valve, the lower part has a heating element, and a water sensor connectable to sound and light indicators at a cabin dash board, and at the bottom there is a drain valve and filter, which is secured at the outlet of the unit. The above purification process depends on causing of some differences in the density of contaminants which contributes towards the settling of heavy impurities and the light contaminants are separated by a wire filter assembly.