What you are describing isn't normal. Something is amiss. I average nearly 27 mpg on the highway and 19 in mixed local driving. I don't exceed 65-70 on the highway and I have a very light foot. The engine isn't undersized but the turbo spools up very quickly and that can use fuel. It can take some effort to retrain one's foot as has been mentioned many, many times over the past four years here. You cannot drive it like many other vehicles because of the turbo. Speed matters and folks out west with high speed limits on the roads who actually drive at high speeds are going to suffer at the pump. The faster one goes, the faster the tank drains. Headwinds affect things, So does a roof-top carrier as it makes what is essentially a brick a bigger brick.

Again, there is some problem here if you're getting fuel economy like you're towing heavy without a big wind-sale trailer behind you. Get things checked out. BTW, the CVT isn't new. The version in the Ascent has been in use for over 13 years now.