Iowa drivers already facing a glut of options at the pump may soon have another decision to make.

President Donald Trump announced Tuesday he has directed the Environmental Protection Agency to begin the process of allowing the sale of E15 fuel year-round.

The rule change on the use of the corn-based fuel could have wide-reaching effects on the state where corn is king.

But it could raise questions for consumers: Namely, is E15 the best thing for my car or the environment?

Here are some of the most commonly asked questions regarding E15:

What is E15?

The majority of gasoline sold in the United States is mixed with 10 percent ethanol. E15 is mixed with 15 percent ethanol.

Ethanol is a grain alcohol that is fermented from corn, wheat, barley or potatoes. In the U.S., it is typically corn-based and primarily used as a gasoline replacement.

How is it made?

Farmers deliver corn to a local ethanol plant. At the plant, the corn is converted to ethanol through fermentation, said Geoff Cooper, CEO of Renewable Fuels Association, an ethanol advocacy group.

The ethanol is then transported by rail cars or trucks to blending terminals, where it is mixed with gasoline and delivered to gas stations across the U.S.

Why is it important to Iowa?

Iowa is the top producer of corn and ethanol in the United States.

If E15 is sold year-round, the number of gas stations offering it will increase, which would be a boost to the state’s economy, Cooper said.

Iowa exports more than 90 percent of the ethanol it produces.

Corn prices are below the cost of production in most areas of the United States, and E15 could result in more corn demand, Cooper said.

Can your car use it?

The Environmental Protection Agency approves the use of E15 in cars made in 2001 and after.

The AAA and oil companies arguing against the change worry that people may accidentally fill their tanks with E15, which can damage vehicles made before 2001.

Cooper said E15 has been used in "billions of miles" across the United States with no issues. He said 90 percent of cars on the road could use E15.

And E15 is typically 5 cents to 10 cents cheaper per gallon than E10, meaning drivers could save a $1 or $2 when filling up at the pump, he said.

What does it do for the environment?

E15 could reduce fossil fuel production and greenhouse gas emissions, according to the EPA. It is produced locally, leading to fewer fossil fuel imports. It could also reduce carbon monoxide emissions, according to the EPA.

At the same time, E15 uses corn, which requires land and water to produce. Depending on the production process, that could produce even more greenhouse gases than some fossil fuels, due to fertilizers used in corn production.

Altogether, the EPA notes that E15 and other biofuels will not reduce greenhouse gases or other pollutant emissions unless it coincides with lessening the production and use of fossil fuels.

Cooper said fuel with ethanol is still better for the environment despite pollutants created during the production of corn.

"It is a cleaner process from beginning to end than producing and using gasoline," he said.

Why isn't E15 available year-round now?

The EPA currently bans E15 from being sold over the summer due to concerns that it contributes to smog. Ethanol advocates say that concern is unfounded.

Cooper said the ban is a 30-year-old regulation that is "outdated," but stagnation in Washington, D.C., has kept the regulation in place.

Where can I purchase E15?

For a full list of gas stations selling E15, visit this list from Iowa Renewable Fuels Association.