Product Reviews
Take Action

Fight for Fair Finance

Tell the administration and Congress to stand up for the consumer watchdog that protects you from financial fraud and abuse.
Take Action
Why Do We Have Campaigns?
We're fighting to ensure you and your family can get a fair deal in the marketplace, especially on the choices that matter most: health care, privacy, automobiles, food, finances and more. Join our campaigns and together, we'll hold corporations and lawmakers accountable.

Ethanol - the challenges with too much of a good thing

Consumer Reports News: March 10, 2008 09:28 PM

The ethanol industry faces a challenge: under the federal Energy Act, passed last December, the industry is required to produce 30 billion gallons of ethanol a year by 2020. Today it produces about 7 billion gallons. And once that much fuel is produced, there is the challenge in ensuring consumers can use it all.

But if ethanol were blended into every gallon of gasoline sold, in the standard 10 percent ratio, it would consume only about half of the 30-billion-gallon requirement.

So far, the Department of Energy (DOE) has proposed two potential solutions:

  • Sell more E85 ethanol, though it is a niche market today.
  • Raise the standard blend from 10 to 15 or 20 percent.

Unlike the standard blend, called E10, which all cars can use, only specially equipped cars can run on E85 ethanol. About five million of those cars are on the road today. According to DOE estimates, it would take 100 million E85 cars to provide a big enough market to absorb the additional 15 million gallons of ethanol in E85. Currently, automakers (mostly those based in Detroit) are building about 1 million new E85-capable cars every year. And they have promised to raise that to about 3.5 million a year by 2012. Still, getting to 100 million E85 cars by 2020 is a tall order. It would also take between 30,000 and 60,000 million gas pumps capable of dispensing E85. Today, there are only about 1,500.

So the DOE, along with some automakers, is testing the potential to raise the standard ethanol blend to 15 or 20 percent, and making that blend universal for all gasoline sold in the United States. In Brazil, all gasoline sold in the country contains at least 25 percent ethanol.

But there are some problems with increasing ethanol blends. Ethanol contains less energy than gasoline, so increasing the amount of ethanol in gasoline will likely result in lower fuel economy. Increasing standard fuel blends from zero to 10 percent ethanol, as is happening today, has little or no impact on fuel economy. In tests, the differences occur within the margin of error, about 0.5 percent. Further increasing ethanol levels to 20 percent reduces fuel economy between 1 and 3 percent, according to testing by the DOE and General Motors. Evaluations are underway to determine if E20 will burn effectively in today's engines without impacting reliability and longevity, and also assessing potential impact on fuel economy.

In our own tests at Consumer Reports, we found that E85 reduced fuel economy by about 27 percent overall in a Chevrolet Tahoe. Interestingly, this is a lower reduction than the fuel's lower energy density would theoretically suggest. General Motors research fellow Kevin Cullen suggests that E85's higher octane rating is allowing the engine's computer control system to advance ignition timing to compensate for the lower energy density in the fuel and making up a little bit of the energy loss.

Andy Karsner, undersecretary for energy efficiency and renewable energy at the federal Department of Energy, says the department is testing to learn whether there is an ideal ethanol blend for fuel economy. Some cars actually returned higher fuel economy on certain midrange ethanol blends ranging from E20 to E40, according to a fuel economy study conducted in November by the ethanol industry and the DOE.

The second problem with raising ethanol blends is evaporative emissions—not the kind comes from the tailpipe, but the kind you smell when filling up your car at a gas station. In engines, ethanol burns cleaner than gasoline does. But low-blend ethanol mixes such as E20 have higher evaporative emissions than either gasoline or E85. So far researchers don't know at what ethanol blend evaporative emissions begin to diminish. And systems to control these emissions have not been developed.

If ethanol is going to play a significant role in reducing U.S. oil dependence, it looks likely that E15 or E20 will become more common. This would mean consumers won't have to buy special cars and look for special pumps for ethanol, meaning every gasoline-engine passenger vehicle would be able to join the effort to reduce dependency on imported oil.

Eric Evarts

Learn more about alternative fuels in our fuel economy special section.

E-mail Newsletters

FREE e-mail Newsletters! Choose from cars, safety, health, and more!
Already signed-up?
Manage your newsletters here too.

Cars News


Cars Build & Buy Car Buying Service
Save thousands off MSRP with upfront dealer pricing information and a transparent car buying experience.

See your savings


Mobile Get Ratings on the go and compare
while you shop

Learn more