Ethanol is available in several different blends for use in conventional and flexible fuel vehicles.
E10 is a low-level blend composed of 10% ethanol and 90% gasoline. It is approved by the U.S. Environmental Protection Agency (EPA) for use in any conventional, gasoline-powered vehicle. The use of E10 was spurred by the Clean Air Act Amendments of 1990 (and subsequent laws), which mandated the sale of oxygenated fuels in areas with unhealthy levels of carbon monoxide. This kicked off modern U.S. ethanol industry growth. Today, E10 is sold in every state. More than 98% of U.S. gasoline contains up to 10% ethanol to boost octane, meet air quality requirements, or satisfy the Renewable Fuel Standard. E10 does not qualify as an alternative fuel under the Energy Policy Act of 1992 (EPAct).
E15 is a low-level blend composed of 10.5% to 15% ethanol and gasoline. E15 is approved for use in model year 2001 and newer light-duty conventional vehicles. Stations must adhere to several EPA requirements and regulations when selling E15. An important requirement is implementation of a misfueling mitigation plan to reduce the risk of vehicles older than model year 2001 refueling with E15. While E15 does not qualify as an alternative fuel under EPAct, it does help meet the federal Renewable Fuel Standard.
E85 (or flex fuel) is an ethanol-gasoline blend containing 51% to 83% ethanol, depending on geography and season that qualifies as an alternative fuel under EPAct. E85 can be used in flexible fuel vehicles (FFVs), which have an internal combustion engine and are designed to run on E85, gasoline, or any blend of gasoline and ethanol up to 83%. FFVs have been produced since the 1990s, and approximately 35 models are currently available. Since FFVs look just like gasoline-only models, visit Fueleconomy.gov to learn how to identify a flex-fuel vehicle or use the Alternative Fuel and Advanced Vehicle Search to find current FFV models. E85 is not approved for use in gasoline-only models.
Intermediate Blends from Blender Pumps
Blender pumps are dispensers that draw and blend fuel from two tanks. For example, a blender pump dispenser can offer three grades of gasoline (regular, premium, mid-grade) by storing regular and premium in two tanks underground. The dispenser is then able to blend the two to offer mid-grade gasoline. Ethanol blender pumps work the same way, with regular gasoline and E85 stored in two tanks. Intermediate blends are for use in FFVs and offer owners more options. Common blends, in addition to E85, include E25 (25% ethanol, 75% gasoline) and E30 (30% ethanol, 70% gasoline). Labels must clearly indicate blender pump fuels for FFVs. Blender pumps are also a legal method to dispense E15 to conventional vehicles, model year 2001 and newer.
The U.S. Department of Energy’s (DOE) Bioenergy Technologies Office funded a project to assess the potential of high-octane fuel (HOF) to reduce energy consumption and greenhouse gas emissions, as well as to understand barriers to its successful market introduction. The project focused on HOF with an ethanol content of 25% to 40% for use in a vehicle engine specifically designed to take advantage of the high octane content of the fuel. Industry continues to investigate the potential of high-octane ethanol fuel. Additional details of the HOF study and publications are available on the Bioenergy Knowledge Discovery Framework.
The Co-Optimization of Fuels & Engines (Co-Optima) initiative is an ongoing DOE-funded multi-national laboratory program evaluating high-octane fuels, including ethanol, to improve vehicle efficiency.