Ethanol is blended with gasoline in various amounts for use in 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 the 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. In 2011, the EPA approved E15 for use in model year 2001 and newer light-duty conventional vehicles. There are several EPA requirements and regulations that stations must adhere to when selling E15. The most significant requirement is an implementation of a misfueling mitigation plan. Misfueling—when the wrong fuel is used in a vehicle—is a concern for conventional vehicles older than model year 2001. While E15 also doesn't 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, and 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%. E85 is not approved for use in conventional gasoline-powered vehicles.
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. They offer FFV owners more options. Ethanol blender pumps are currently concentrated in the Midwest and the most common offerings, in addition to E85, are E25 (25% gasoline, 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 of 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 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. The work was conducted by Argonne National Laboratory, the National Renewable Energy Laboratory, and Oak Ridge National Laboratory. 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, in an effort to improve vehicle efficiency.