What is the purpose of the 'Eco' button on the Kia Rio?

I noticed a button labeled 'Eco' on my Kia Rio. What does it do and when should I use it?

The 'Eco' button adjusts the car's performance for better fuel efficiency. It's best to use it when driving in heavy traffic or on long trips.

The 'Eco' button can also be used to conserve fuel during city driving or when stuck in stop-and-go traffic. Just make sure to turn it off when you need more power, such as when merging onto a highway.

I've found that using the 'Eco' button has improved my gas mileage by 10-15%. It's definitely worth using on a regular basis.