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Ethanol

Intermediate Ethanol Blend Research

Several government and industry groups are researching the effect of intermediate ethanol blends on the exhaust and evaporative emissions, driving performance, and engine and fuel system components of gasoline-powered automobiles. Researchers are also investigating the effects of intermediate blends on small engines such as those used in lawn equipment, motorboats, and off-road vehicles. Because the fuel systems in small engines are not as advanced as those in automobiles, they react differently to the use of ethanol-blended fuel; the increased oxygen content in intermediate ethanol blends could cause operational and safety issues in small engines.

The U.S. Department of Energy (DOE) and its National Laboratories are evaluating automotive emissions and catalyst durability as well as the performance and durability of small engines. The first report on this research is available: Effects of Intermediate Ethanol Blends on Legacy Vehicles and Small Non-Road Engines, Report 1 (PDF 1.5 MB). Download Adobe Reader. Following are highlights from the report:

  • Testing was performed on 13 popular late-model vehicles and 28 small non-road engines

  • Test fuels were E0 (0% ethanol, 100% gasoline), E10, E15, and E20

  • For the vehicles:

    • Fuel economy decreased commensurately with increasing ethanol content, e.g., vehicles fueled with E20 averaged 7.7% lower fuel economy compared with those fueled with E0.

    • Regulated emissions were largely unaffected by fuel ethanol content; some unregulated emissions increased with higher ethanol content.

    • Catalyst temperatures were cooler or unchanged with higher ethanol content under normal conditions.

    • At wide-open throttle, about half the vehicles had higher catalyst temperatures when fueled with E20.

    • Informal observations showed no driveability differences as a result of higher ethanol content.

  • For the small non-road engines:

    • Performance varied considerably among the engines tested, regardless of the fuel used.

    • Higher ethanol content increased nitrogen oxides (NOx) emissions but decreased hydrocarbon and carbon monoxide emissions.

    • Engine and exhaust temperatures increased with higher ethanol content.

    • Three handheld trimmers operating with higher ethanol blends demonstrated higher idle speed—resulting from a leaner fuel:air mixture, which can be adjusted in some engines—and experienced unintentional clutch engagement.

    • Ethanol content did not affect durability in commercial engines and more sophisticated residential engines.

    • The effect of higher ethanol content on the durability of smaller, less expensive residential engines was unclear because a number of these engines failed.

    • In 2-cylinder engines, temperature and emissions variations due to differences in air-fuel distribution between cylinders suggest multi-cylinder, open-loop engines might be more sensitive to ethanol blends.

    • Although not specifically characterized, no obvious materials compatibility issues were noted.

The Coordinating Research Council (CRC)—an automotive and petroleum industry research organization—is researching areas such as evaporative emissions, fuel system component durability, fuel volatility, and catalyst durability. See the following reports and visit the CRC Web site for results of recent intermediate ethanol blend research:

In 2005, Minnesota came to the forefront of efforts to use intermediate blends by passing a law mandating use of 20% ethanol in the state's gasoline by 2013 (if certain conditions are met—see Ethanol Blend Mandate under Minnesota Incentives and Laws). The State of Minnesota and the Renewable Fuels Association are sponsoring research on E20 in support of the mandate. Their research areas include automotive exhaust and evaporative emissions, materials compatibility, driveability, and air-quality effects. Preliminary research results suggest that E20 presents no immediate problems for current automotive or fuel dispensing equipment (which is listed for E10 use only by Underwriters Laboratories) and that vehicles fueled with E20 operate with similar power and performance as those fueled with E10. To learn more, see the Minnesota Department of Agriculture's Ethanol Web site. This early-stage research is not conclusive; ongoing DOE research will help clarify the effects of E20 use.

The Australian government has sponsored research on intermediate ethanol blends in automotive and small-engine applications. Find the reports on the Department of the Environment and Water Resources Fuel Quality Publications page.

AllSAFE advocates thorough research on ethanol-blended fuels. AllSAFE represents industries related to recreational boats, marine engines, chainsaws, lawnmowers, motor vehicles, motorcycles, all terrain vehicles, snowmobiles, and generators. The Technical Paper on the Introduction of Greater than E10-Gasoline Blends (PDF 75 KB) summarizes AllSAFE's concerns about using intermediate ethanol blends. Download Adobe Reader. The National Marine Manufacturers Association, a member of AllSAFE, hosts a small library of documents related to ethanol blends.