E-15, or 15% Ethanol is a blend of gasoline that contains no less than 10% and up to 15% ethanol (by volume). E-15 gasoline was approved by the EPA for use in cars that were manufactured after 2001. However, the EPA prohibited the use of E-15 in any 'non-road" vehicles, including outdoor power equipment.
Gasoline that is blended with more than 10% ethanol is illegal for use in outdoor power equipment. Using E-15 gasoline in outdoor power equipment could result in permanent damage to the engine and might void the manufacturer's warranty.
So remember to always "Look Before You Pump" when refueling your outdoor power equipment to ensure that you are using fuel that contains no more than 10% ethanol. Use E-10 fuel or less.