Yes. My buddies Civic is the same. Not because of aerodynamics but weak power plant. I babied her Grand in our way to vacation last year and held her at 65 entire way. I achieved mid 20s as well. On way home I ran 75-80 and was getting her typical 14-16. But man I just wanted to get home. Lol.I told a co-worker about the bad gas mileage at 80mph today and she said her grandma's Rubicon (I think late 90s) was the same way. Anything above 70mph and you're just killing the gas mileage. The best gas mileage I ever got was 23mpg and that was driving 65mph-70mph the entire tank. But it all makes sense because it takes 8 times the horsepower to go twice as fast. It just gets exponentially worse with gas mileage the faster you go.
I did also notice in my JK a drop in mileage and oil consumption (2-3 quarts / 3,000 miles) over the past year or so. I ended up changing out my PCV valve. My mileage is back and oil is holding steady now over the past few weeks..