The use of ethanol as a fuel in North America has significantly increased over the past decade. Today, approximately 80 percent of all retail gas stations in the United States blend gasoline with up to 10 percent ethanol (E10).  With the introduction of ethanol, however, comes the introduction of new issues to deal with.  Phase Separation, caused when water enters a tank of ethanol-blended fuel, is increasingly more common and more dangerous to station owners. This article discusses the dangers of phase separation and the methods of early detection.