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Ethanol Flexible Fuel Vehicle and Infrastructure Key Terms

Photo of a flex fuel vehicle

What are the key terms to know when discussing ethanol flexible fuel vehicles (FFVs) and their fueling infrastructure?

It is important to know how to "talk the talk" when it comes to FFVs. Becoming familiar with the terms below will help you better understand these vehicles and the associated fueling infrastructure so that you can ask the right questions and make informed decisions:

FFV: An FFV is a vehicle that has an internal combustion engine and can run on E85 (defined below), gasoline, or a mixture of the two. Except for fuel system and powertrain adjustments that allow the vehicles to run on higher ethanol blends, FFVs are virtually identical to their conventional gasoline vehicle counterparts; however, drivers can expect a slightly lower fuel economy when driving on ethanol compared to gasoline, depending on the ethanol blend.

Types of Ethanol

Ethanol can be categorized into two main types based on the feedstocks used for its production:

  • Starch- and sugar-based ethanol: Produced from feedstocks like corn, wheat, milo, and sugarcane, starch- and sugar-based ethanol makes up the majority of all domestic ethanol production. In fact, corn is the most common ethanol feedstock in the United States. This type of ethanol is manufactured through dry- or wet-mill processing. More than 80% of ethanol plants are dry mills due to lower capital costs. Dry-milling consists of grinding corn into flour and fermenting the mixture, resulting in distiller grain and carbon dioxide co-products. Wet mills separate the starch, protein, and fiber in corn prior to processing these components into products, such as ethanol.

  • Cellulosic ethanol: Produced from feedstocks like crop and wood residues, dedicated energy crops, and industrial and other wastes, cellulosic ethanol offers advantages over starch- and sugar-based feedstocks (e.g., no food-versus-fuel concerns). Feedstock components include cellulose, hemicellulose, and lignin. Because it is more challenging to extract sugars necessary for ethanol production from these feedstocks, cellulosic ethanol is more difficult to manufacture than starch- and sugar-based ethanol. This type of ethanol can be produced through two conversion pathways:

    • Biochemical: Feedstocks are pretreated to release hemicellulose sugars and then undergo hydrolysis to break cellulose into sugars. Sugars are fermented into ethanol, and lignin is recovered and used to produce energy to power the process.

    • Thermochemical: Heat and chemicals are added to feedstocks to create a mixture of carbon dioxide and hydrogen, also known as syngas. Syngas is then mixed with a catalyst to produce ethanol.

Ethanol Blends

The following ethanol blends can be used in conventional gasoline vehicles (note model year restrictions for E15):

  • E10: (10% ethanol, 90% gasoline) – E10 is classified as "substantially similar" to gasoline by the U.S. Environmental Protection Agency (EPA) and is legal for use in any gasoline-powered vehicle. More than 95% of the U.S. gasoline supply contains up to 10% ethanol to boost octane, meet air quality requirements, or satisfy the Renewable Fuel Standard (RFS2), which calls for 36 billion gallons of biofuels to be blended into transportation fuel by 2022. E10 must meet ASTM D4806 fuel specifications. ASTM International develops specifications for conventional and alternative fuels to ensure proper vehicle operation and safety.

  • E15: (15% ethanol, 85% gasoline) – E15 is legal for use in model year 2001 and newer vehicles; however, there are several EPA and state agency requirements and regulations stations must adhere to when selling E15. Fuel producers that market E15 are required to individually register with EPA. While E15 does not qualify as an alternative fuel under the Energy Policy Act of 1992 (EPAct), it does help meet RFS2. E15 must meet fuel specifications laid out in ASTM D4806 and cannot be used in motorcycles, heavy-duty vehicles, off-road vehicles, or off-road equipment.

The following ethanol blends above E15 should only be used in FFVs due to material and compatibility issues associated with the high alcohol content of ethanol:

  • Mid-level blends: Blender pumps (defined below) can create various other ethanol blends between E15 and E85 (also defined below). E20 (20% ethanol, 80% gasoline) and E30 (30% ethanol, 70% gasoline) are the most common blends selected. Mid-level ethanol blends must meet fuel specifications laid out in ASTM D7794.

  • E85: E85 is considered an alternative fuel under EPAct and can contain 51% to 83% ethanol, depending on geography and season. This variance in ethanol content is allowed to ensure proper starting and vehicle performance in geographic locations where cold temperatures can affect fuel properties. Though dependent on the blend, drivers can expect about 27% less energy per gallon than gasoline, resulting in a corresponding reduction in fuel economy, when using E85. E85 must meet ASTM D5798 fuel specifications.


Low-level ethanol blends up to E10 have already been incorporated into the majority of the U.S. gasoline supply, and fueling stations that supply these blends are not required to update their fueling infrastructure. Ethanol blends above E10, however, do require specific ethanol-compatible equipment, including:

  • Dispensers: E85 and blender pump dispensers require specialized metals and seals to perform with high concentrations of ethanol. Permitting authorities typically require all ethanol dispensers to be UL-listed for the ethanol blend dispensed.

  • Hanging hardware: Hanging hardware, including hoses, nozzles, swivels, and breakaways, used to dispense ethanol blends should use ethanol-compatible materials. Permitting authorities typically require hanging hardware to be UL-listed for the ethanol blend dispensed.

  • Storage tanks: EPA guidance allows underground storage tank (UST) manufacturers to provide a statement of compatibility for their products with specific biofuels blends. All tank manufacturers have issued statements of compatibility with ethanol blends. For a list of UST manufacturers and their ethanol-compatibility statements, refer to the Clean Cities Handbook for Handling, Storing, and Dispensing E85 and Other Ethanol-Gasoline BlendsPDF.

Most stations that dispense mid-level blends also have the following:

  • Blender pump: This type of fuel dispenser offers FFV owners a variety of ethanol-blended gasoline products between E15 and E85. Blender pumps draw fuel from two separate storage tanks (E10 and E85) and can dispense preprogrammed blends of those fuels. Blender pumps also may be used to dispense E15 legally. Note that blender pumps currently are offered only at select fueling stations and are mainly concentrated in the Midwest. The Alternative Fuels Data Center (AFDC) Fueling Station Locator includes details about E85 stations with blender pump availability.

Additional information on FFVs, ethanol feedstocks, and infrastructure can be found on the AFDC Ethanol page.

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