Flex fuel is E85, the Kia should be fine on E15.
Praying Medic is currently tweeting about this: In April, Q dropped hints about a scandal involving cities in Guangdong province, China that we would learn about in the future and now, that scandal is being made public... The Shenzen Stock Exchange and google.
https://twitter.com/prayingmedic
The manual says not to use e15. Voids the warranty. Look at your car manuals, not some guy on the internet. That was the point of the post.