E-10, 90 percent gasoline, 10 percent ethyl alcohol, uses the same alcohol we enjoy drinking, but with a bit of poison added. The alcohol is beneficial in many (especially cold) climates. It oxygenates the fuel, increases its octane number, enhances the combustion process in cold weather and reduces tailpipe emissions. (This is nothing new here, as it was doing the same thing in the 1920s and '30s; see Sidebar.) E-10 basically does what MTBE did before it was widely removed from use because of its ability to infiltrate the water table and make drinking water taste terrible. Most marine engines can burn the E-10 with little difficulty, provided the boat does not have fiberglass fuel tanks. (E-10 fuel may dissolve a fiberglass fuel tank and the liberated material can ruin the engine and your day).