October 6, 2015 - Ethanol’s inherently high octane rating makes it attractive for meeting fuel economy and greenhouse gas targets and renewable fuel mandates, according to an Oak Ridge National Laboratory report. Although ethanol has two-thirds the energy density of gasoline, its higher octane – an anti-knock index – rating allows for more aggressive engine design, which can improve efficiency. “High-octane fuels can create additional demand for large amounts of ethanol and enable improved fuel economy in dedicated vehicles,” said Tim Theiss of ORNL’s Sustainable Transportation Program. Researchers expect efficiency gains that offset the lower energy density to occur with blends of between 20 and 40 percent ethanol. They also point to potential benefits of about a 30 percent reduction in greenhouse gas emissions, vehicle efficiency gains of up to 10 percent and significant increase in ethanol demand with a corresponding decrease in petroleum use.