E85 Specifications

ASTM International developed specifications for E85—a gasoline-ethanol blend containing 51% to 83% ethanol—to ensure proper vehicle starting, operation, and safety. The table below shows the ASTM D5798-11 Standard Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines. Fuel suppliers should guarantee their product meets these standards and list meeting them as a requirement in their supply contracts.

Like gasoline and diesel fuel, E85 is seasonally adjusted to ensure proper starting and performance in different geographic locations. For example, E85 sold during colder months often contains less than the allowable 83% ethanol to produce the necessary vapor pressure for starting in cold temperatures. For this reason, E85 fueling site operators typically can't carry over summer-blend E85 in the winter months. They must instead "blend down" any remaining summer fuel to meet ASTM specifications for winter fuel. This can be done with relative ease by adding additional gasoline to the storage tank. On the other hand, there's no concern with carrying over winter fuel into the summer months because flexible fuel vehicles can operate on any blend of E85 and gasoline in warm weather. For retail service stations, seasonal fuel adjustments are handled automatically at the wholesale fuel terminal.

Refer to the Handbook for Handling, Storing, and Dispensing E85 for local seasonal blending requirements (this guide will soon be updated with the ASTM D5798-11 Standard Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines).