In June 2018, the U. S. Environmental Protection Agency approved the large scale blending of bio-derived isobutanol into gasoline at concentrations up to 16%. This newly approved oxygenate has multiple advantages over ethanol, such as lower volatility, 3 lower hydroscopicity, and higher energy density, while providing similar knock resistance. Relative to larger alcohol additives, isobutanol also shows longer ignition delay times with lower CO and NO x emissions, indicating it could help boost the octane numbers of fuel while lowering other emissions. With this approval, isobutanol could become a major component of transportation fuel in the United States.