Gas oil or diesel fuel (French: Gazole) is used as fuel in diesel engines and thermal installations. Its range of hydrocarbon is between C14-C20 and even C25 with a boiling point range of 385-250 ͦ C. Gas oil mainly consists of three groups of paraffinic, naphthenic and aromatic with minimum flash point 54 ͦ C and maximum pour point of 0 °C. Its density is 15.6 ° C which equals to 820-860 kg / m3. Cetane number is the most important feature that it should be more than 50 so that engine can work easily and silently.