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E85 and gas mileage: Where lies the truth?

Agriculture.com Staff 02/10/2016 @ 6:23pm

As consumers across the country hear more about flex-fuel vehicles and corn-based ethanol, a mini-battle is brewing over just how big an impact ethanol has on a car's fuel economy.

Ethanol supporters and detractors agree that ethanol reduces gas mileage, because of its lower energy content. But by how much? The Iowa Corn Growers E85 Web site says that if you have a flex-fuel vehicle and burn E85 (85% ethanol, 15% regular gasoline), you'll experience a gas mileage drop of 5-15% compared with regular gasoline. Taking the middle, a car that gets 25 mpg on regular gas would get 22.5 mpg on E85.

Others say the gas mileage penalty for E85 is more severe. For instance, a story in USA Today this week told its millions of readers that the E85 mileage penalty is 28%. That means your 25 mpg car now only gets 18 mpg if you flex to E85.

While many consumers might willingly sacrifice 2.5 mpg in order to burn American-produced renewable ethanol, will they sacrifice 7 mpg? At that rate, a tank full (about 15 gallons) of regular gasoline would take you 100 miles farther than a tank of E85.

As with most issues, the truth on this one may lie somewhere in the middle. We called Dale Schroeder, administrator of fleet vehicles for the Iowa Department of Administrative Services. That state has over 1,000 E85 cars in its vehicle fleet (mandated by the governor and the state legislature). Iowa started using E85 vehicles in 1991. So, we asked Schroeder, what is the impact on gas mileage of E85 in real-world conditions?

"In the first few years, I kept very close track of this," says Schroeder. "We had a 17% reduction in fuel economy with E85."

Still, that answer is not so neat and tidy. Most people -- including state workers -- can't always put E85 in a car. There are still only a few hundred pumps nationwide that dispense E85. So, at least until recently, few flex-fuel cars have burned E85 exclusively. They will burn a tank of E85, then a tank of the more readily available E10, then another E85. As a result, the 17% reduction that Schroeder reports is based on his fleet burning about 55% E85, and 45% E10. "I was told that the [mileage] reduction could be 25%, so I didn't think 17% was too bad," he says.

"I know the technology on these E85 engines is better now than it was then, but I don't know that it's dramatically different," Schroeder says.

Unfortunately, the cost of E85 to the state of Iowa is higher than the cost of E10. On Friday, May 5, Schroeder said the cost of E10 at the state's bulk tank, untaxed, is $2.20 a gallon. E85 is $2.77. Schroeder theorizes that the difference is because of the current high demand for ethanol, particularly in places like California where ethanol must replace other fuel additives.

"Our governors and our state legislature have long supported ethanol," says Schroeder. "It creates jobs in Iowa, it promotes energy independence, and it's a cleaner fuel. I want us to continue to use [E85] in our state vehicle fleet. In the next year and half, we're going to move rapidly in that direction."

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