What type of fuel for a 2013 ford focus se? Flexfuel?

It says "flex fuel" i know that has something to do with running on ethonol. Its a rental car and ui don't want to put regular 87 octane unleaded if it needs something else. What's so special about the flex fual thing? Its the se model and the sedan. Automatic transmission. This may be a dumb question but seriously is it fine to just use regular unleaded?

Regular is fine

A flexible-fuel vehicle (FFV) or dual-fuel vehicle (colloquially called a flex-fuel vehicle) is an alternative fuel vehicle with an internal combustion engine designed to run on more than one fuel, usually gasoline blended with either ethanol or methanol fuel, and both fuels are stored in the same common tank.

Flex fuel just means it can take E85, which is 85% alcohol, but it will do fine on regular.

If it says Flex Fuel on the badge, you can use regular unleaded, regular unleaded with 10 or 15 percent ethanol, or E85 (which is 85 percent ethanol). You don't need higher grades.