I just took a long road trip in my Niro and I thought I would share some thoughts on how it went.
We went to visit my wife's family in Tallahassee, FL. We're in Phoenix, AZ so it was a pretty long drive. We did it in two days. The first day was to San Antonio. Leaving Phoenix the next major city you come to is Tucson. Right away I noticed that the mileage was down a bit, even lower that the rated highway mileage. First off, I was going 80MPH, second, parts of the highway are up and down and that was my first introduction to hills killing my mileage. I got in the low 40's in MPG when I did my first fill up in Las Cruces, NM. The rest of the way to San Antonio was very hilly. Once you get about 2 hours outside of El Paso the terrain gets very unfriendly to mileage and I ended up getting in the mid 30's on my mileage during that leg of the trip. Still, anyone driving a regular gas engine would have fared much worse.
On day two, most of the driving was flat and level to Florida. For the better part of the day we got in the mid 40's in mileage going about 75MPH.
As far as our load, we had two adults and an 8 year old. We packed fairly light so there weren't a bunch of heavy suitcases back there. One medium suitcase, a backpack and a few other items.
Some overall observations... The car really does well going up hills. I was surprised to be honest. I had no trouble at all. The electic motor and gas motor working together do quite well. Also, the car breaks well. I had one particular instance where I had to break pretty urgently when traffic was stopping and I was shocked that it didn't lock up. It stopped very fast.
The car was very comfortable. We drove for two long days each direction and we didn't feel beat up quite as much as we usually do. Someone else mentioned on here some irregularities in the cruise control. I can verify that I also had issues with the cruise control. When doing a "resume", it would sometimes resume at a slower speed than before and sometimes would resume at a faster speed than before. Most of the time it was slower. It rarely worked correctly.
Driving in the city we ended up right at about 51MPG (according to the dashboard readout.) The slower speeds that we drove really made a difference in the mileage. We rarely went faster than 50 MPH in the city. Speed is the big factor in getting good mileage.
The last thing I wanted to mention is that the in-dash mileage was consistently 3-4 MPG higher than what I actually got when refilling my tank. It was a little disappointing to be honest. It always said a higher number than what I really got.
Other than those few items, overall I'm very happy. It was a great experience. I drove round trip for just under $200 in gas. (Which is why I didn't fly)