ASTM D5798 Standard Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines
4. Ordering Information
4.1 The purchasing agency shall:
4.1.1 Indicate the season and locality in which the fuel is to be used,

4.1.2 If requested, ensure that the ethanol concentration meets the requirements for an alternative fuel for federal fleets.
4.1.2.1 The composition of alternative fuels in the United States is regulated by various government agencies and regulations including the U.S. Department of Energy (DOE) and U.S. Environmental Protection Agency (EPA). With regard to fuel properties including volatility, this specification can be more or less restrictive than DOE or EPA rules, regulations and waivers. To qualify as an alternative fuel for federal fleet use in the United States, the ethanol blend is required to meet the U.S. Department of Energy's definition of alternative fuels, enacted under the Energy Policy Act of 1992 (Title III, Sec. 301). For ethanol, the Act defines "alternative fuel" as a mixture containing denatured ethanol at a volume of "85 percent or more (or such other percentage, but not less than 70 percent, as determined by the Secretary, by rule...)". Correcting for denaturant content, a blend of 70 to 85 volume % denatured fuel ethanol contains 68 % to 83 volume % ethanol as measured by Test Method D5501. The U.S. government has other programs and definitions for alternative fuels.

4.1.2.2 Users of this specification are advised to check with the applicable regulatory agency for specific alternative fuel requirements.

5. Ethanol Fuel Blends Performance Requirements
5.1 Ethanol Fuel Blends shall conform to the requirements of Table 1.
5.1.1 The components used to produce Ethanol Fuel Blends are limited to denatured fuel ethanol and hydrocarbon blendstock as defined in 5.2.

5.1.2 The intentional addition of lead or phosphorus compounds to ethanol fuel blends is not permitted.

5.2 Hydrocarbon Blendstock blended with the denatured fuel ethanol shall meet the requirements of Table 2.
5.2.1 The hydrocarbon blendstock may be unleaded gasoline, gasoline blendstock for oxygenate blending (BOB), natural gasoline or other hydrocarbons in the gasoline boiling range.

5.3 Vapor pressure is varied for seasonal and climatic changes by providing four vapor pressure classes for ethanol fuel blends.
5.3.1 Class 1 encompasses geographical areas with 6-hour tenth percentile minimum ambient temperature of greater than 5 °C (41 °F).

5.3.2 Class 2 encompasses geographical areas with 6-hour tenth percentile minimum ambient temperature of greater than -5 °C (23 °F) but less than or equal to 5 °C (41°F).

5.3.3 Class 3 encompasses geographical areas with 6-hour tenth percentile minimum ambient temperature greater than -13 °C (9 °F) but less than or equal to -5 °C (23°F).

5.3.4 Class 4 encompasses geographical areas with 6-hour tenth percentile minimum ambient temperature less than or equal to -13 °C (9 °F).

5.3.5 There is a 10 % probability that the highest temperature of the six coldest consecutive hourly temperature readings of a 24 h day will be colder than the 6 h tenth percentile minimum ambient temperature.

5.3.6 See 5.4.4 and 5.5.2 for seasonal and geographical distributions.

5.4 Regulatory and Other Requirements in the United States:
5.4.1 Ethanol content requirements for ethanol alternative fuel blends can be found in 4.1.2.1.

5.4.2 The denaturant for the denatured fuel ethanol used in making ethanol fuel blends shall meet the requirements of Section 5 in Specification D4806.

5.4.3 Ethanol fuel blends of any volatility class shall meet certain U.S. Environmental Protection Agency (EPA) regulations for unleaded gasoline. See Appendix X2.

5.4.4 The United States seasonal and geographical distribution for the four vapor pressure classes is shown in Table 3.

5.5 Regulatory and Other Requirements Outside the United States:
5.5.1 Users of this specification are advised to consult with the applicable regulatory agency for specific requirements for their jurisdictions.

5.5.2 Users of the specification in geographical areas outside the United States need to determine the 6-hour tenth percentile minimum ambient temperatures for their geographic areas and times of year in order to select the appropriate classes of fuel.

6. Workmanship
6.1 The finished fuel blend shall be visually free of sediment, suspended or undissolved matter. It shall be clear and bright at the fuel temperature at the point of custody transfer or at an alternative temperature agreed upon by the purchaser and seller.

NOTE 1 - Finished fuel should be resistant to phase separation or undissolved matter at the lowest temperatures to which it is likely to be subjected, dependent on the time and place of its intended use. See Specification D4814, Table X7.1 for guidance.

NOTE 2 - Solubility is temperature dependent. As this fuel cools some high molecular weight additives can become insoluble.

6.2 The specification defines only a basic purity for ethanol fuel blends. The product shall be free of any adulterant or contaminant that can render the material unacceptable for its commonly used applications.
6.2.1 Manufacturers and blenders of ethanol fuel blends shall avoid ethanol (for example, improperly recycled ethanol), or denaturants and hydrocarbon blend components contaminated by silicon-containing materials, or both. Silicon contamination of gasoline, denatured ethanol, and their blends has led to fouled vehicle components (for example, spark plugs, exhaust oxygen sensors, catalytic converters) requiring parts replacement and repairs. Test Method D7757 is a procedure for determining silicon content but no specification limits have been established for silicon.