The Answers on Ethanol

E85 consists of up to 85% ethanol mixed with gasoline. It's a cleaner-burning, higher-octane fuel that can help offset the rising demand for oil. GM cars and trucks account for 3 million of the 7 million flex-fuel vehicles (Fig. 5) in the U.S. In 2007, the production and use of ethanol in the U.S. reduced oil imports by 228 million barrels. Since E85 is not readily available everywhere (approximately 1,500 E85 fueling stations nationwide), there still are many questions about it, how it's made, and its benefits. Here are a few answers.

Is E85 always made from corn?

GM is working with several companies on biofuels made from non-grain sources, including cellulosic ethanol made from agricultural and municipal solid waste --including old tires -- and second- and third-generation biofuels made from plant and wood wastes. In the U.S. alone, there is more than 1 billion tons of biomass that can be converted into fuel annually. 

Most regular gasoline is 10% ethanol (E10), so can E85 be used in any vehicle?

Only vehicles designated for use with E85 should use E85 blended fuel. These vehicles are certified to run on up to 85% ethanol and 15% gasoline. To adjust for the alcohol (ethanol) content of the fuel in the tank, earlier flex-fuel vehicles used an alcohol sensor to detect the ethanol/gasoline ratio. A new way to determine the alcohol content is through the use of a flex-fuel algorithm that temporarily closes the canister purge valve and monitors information from the closed loop fuel trim system to calculate the ethanol content.

In addition, flex-fuel vehicles have a modified fuel delivery system -- including the fuel tank, fuel lines, fuel injectors, computer system, and instrument cluster gauges -- to tolerate the alcohol in E85.

Do not use fuel containing greater than 10% ethanol in non-E85 designated vehicles. This may cause driveability issues as well as increased fuel system corrosion.

What is E85's impact on vehicle fuel economy?

E85 gets 20% to 25% fewer miles per gallon compared with regular unleaded gasoline. However, regular unleaded gasoline has an 87 octane rating compared with an octane rating of 96 for E85, which can provide better engine performance. Premium gasoline with a lower octane rating (typically 93) often sells at a higher price.

Is E85 better for the environment?

Regarding vehicle emissions, according to a recent study conducted by Argonne National Laboratory, ethanol use in the U.S. in 2007 reduced CO2-equivalent greenhouse gas (GHG) emissions by approximately 10.1 million tons. This is equivalent to removing more than 1.5 million cars from the road.

E85 contributes to a 20% reduction is ozone-forming pollution and 30% reduction in GHG.

Does it take more energy to produce ethanol than it provides?

Ethanol requires less energy to produce than it delivers as a fuel. The new energy balance of making fuel ethanol from corn yields about one-third more energy for automotive fuel than is used to grow the grain.

The next generation of cellulosic ethanol can produce up to 7.7 times as much energy as what is used to make the fuel compared to conventional gasoline.

Can ethanol really reduce oil imports?

In 2007, the production and use of ethanol in the U.S. reduced oil imports by 228 million barrels, saving $16.5 billion from being paid to foreign countries.

- Thanks to Alan Adler and Jay Dankovich