Ioniq is rated at 58 miles per gallon in combined city and highway driving for its base version, called the Blue. That will not only be the highest rating of any car without a plug, but will best Prius by 2 mpg. The more upscale versions of Ionic are rated at 55 mpg combined.
http://www.usatoday.com/story/money/cars/2017/02/24/review-hyundai-ioniq-hybrid-aims-top-gas-mileage/98228424/