Blended gasoline generally gets cheaper as ethanol content rises, as well. Thus, a move to introduce year-round E15 might result in lower prices at the gas pump, which motorists are sure to enjoy.
However, E15 will also likely result in your vehicle returning worse fuel economy. Increasing ethanol content in a gallon of gasoline also reduces its energy density, which means a gallon of gas won’t get you as far as it would if it had less ethanol. Flex-fuel vehicles, which are capable of operating on gasoline that’s up to 85 percent ethanol (E85), run less efficiently than they do on regular gas, sort of negating E85’s lower cost.
Read the article at CNET.