Petroleum, as well as its middle distillate fractions (boiling between 150-400 degreesC), shows a tendency to crystallize paraffin molecules whenever the temperature is lowered below the cloud point. Paraffin deposition may occur in storage tanks, pipelines, or conduits, this leading to the impairing of fluid pumping, with even filter plugging of diesel engines. Such a drawback may be overcome by the addition of chemical compound.