In my Limited AWD I averaged about 27 MPG on a just-completed 1200 mile trip. The majority of the miles were on the highway in ECO mode, typically going about 75 mph. Winds were light and the terrain was flat, so those factors didn't play a big role in the outcome.
Closer to home, commuting to work and running errands in more stop-and-go driving, I'm averaging about 22 MPG.
On right side of steering wheel, button on top left. symbol on it looks like pages. use the little lever just below that on each page to see what you can learn about MPG, miles traveled, what you want shown on the center of display.
There is all kinds of information
I have found that the on board mileage is about 2 mpg higher when I compare the manual way of calculation. All 6 of my Hyundais have been this way, but my 2016 Mazda Miata is almost always the same when compared. I think Hyundai want’s everyone to believe they are getting good gas mileage.
I drive with a light foot and do not speed or jack rabbit start or stop. According to my mileage readout, I'm averaging 15mpg in the city and 19 on the freeway. And that's an average. This is much lower than the book. Should I take it in and have the gage checked?
Try to compare by checking mileage compared to how much gas you use in the course of several fill ups.
Also do you do a lot of city driving where you set a numerous red lights? that is really bad on mpg
One thing to check is how you have the milage computer set up. Would recommend setting to reset on start /stop.
The next to keep in mind that a true CR or EPA city estimate is a defined mix of rural driving with a certain amount of stops over precise milage, not stuck in bumper to bumper traffic or stop lights at every block. Highway has its own definitions.
I only really pay attention to highway driving averages and there is a milage guage in addition to average number is displayed. You will see for example that there are brief times where milage gauge will show as much as 50mpg,
As to averages on 30 minute to 5 hour drives i have taken which have not been diluted too by the local portion of the trips I see 24 to 29 MPG and the most common averages I see are 25, 26, 27 MPG, I believe these numbers are pretty close. My driving speed on most highways 60s and 70s generally. "True City driving is going to rot in any car"