The U.S. Environmental Protection Agency (EPA) currently allows gasoline to include up to 10 percent ethanol (E-10), a fuel additive made from corn or other biomass sources. The ethanol industry wants the EPA to increase the amount to 15 percent.
The problem with this is that the increase ethanol can cause a number of bad side effects when burned in older engines. Ethanol attracts water. In turn, the resulting condensation can corrode the fuel lines, fixtures and tank components (steel, rubber, aluminum, etc). We're talking rust, clogging and deterioration. Many newer engines and parts have been designed to be more compatible with alcohol fuels, and E-15 will not be an issue. But E-10 has been a problem for some current and older models, and E-15 may be worse. Many in the auto industry have cautioned the EPA to do more science before it rules on the request.
Why does it matter? The fact is gasoline without ethanol may eventually become scarce or non-existent when you pull up to the pump. We also face an education curve, for many people who already ignore the "contains 10 percent ethanol" sign will not understand that 15 percent may cost them a pretty penny in repair bills.