Energy is the most important element for economic development and security of each country. Fossil energy sources are mostly used in the world nowadays. According to the researchers, fossil fuels will be depleted over the time of exploitation. Beside economic problems, environmental pollution is the top concem of the globe. Therefore, the research scientists are always looking for other sources of energy in order to gradually replace fossil energy, for example biofuels. The .report presents research results to enhance the octan number of low octane number gasolines such as RON 90 and to decrease air pollution. Adding methylcyclopentadienyl manganese tricarbonyl (MMT) (at the concentration of 19mg/L) and butanol (11 percent volume) to RON 90 gasoline has increased octane rating to 91.1 while other specifications such as Mn, oxygen, benzene contents and oxidation stabitity remained at the accepted levels as required by the TCVN 6776:2005 standards.