30 days from today, E15 will no longer be marketable for most automobiles and light-duty vehicles. Without an exemption from the Reid Vapor Pressure (RVP) limits imposed on motor fuel by the Clean Air Act, it cannot be sold during the summer period of 1 June-15 September. RVP is the measurement of evaporation volatility of fuels, a process that causes smog. Summer fuels must have an RVP of 9 pounds per square inch (psi) or less, and E15 exceeds that. The RVP of biofuels blended into gasoline is 10, exceeding the standard by 1 psi. E10 has an exemption, but E15 does not. Last year, however, the EPA allowed E15 to be sold between 1 June and 15 September if labeled as a “flex fuel” to be legally used by flexible fuel vehicles (FFV...