Methods and systems for converting petroleum based oil into fuel generally include forming a conversion mixture of an alcohol and a base, adding the conversion mixture to petroleum based oil (such as crude oil, used oil, used motor oil, and new motor oil) to form a reaction mixture, adding a high nitrate compound and an amino acid the reaction mixture, ozonizing the reaction mixture. The result may include a three phase system in which the bottom phase is asphalt oil, the middle phase is diesel fuel or jet fuel, and the top phase is sulfuric acid. The three phases may be separated to obtain the final diesel fuel or let fuel product. Additional cooling and/or filtering processes may be utilized to complete and/or optimize oil conversion.