That's a pretty darn huge gap between how people normally drive, and the EPA numbers (which I did match, doing 5 under, and pissing everyone on the freeway off as I coasted up hills and gently accelerated down them).
There isn't a vehicle out there that can match EPA numbers when driving 75-80 mph. Which isn't surprising to those who know the EPA hwy test cycle has an average speed of 48.3 mph and a top speed of 60 mph. I'm not sure why this surprises you as the shape of a utility vehicle is not known for it's good aerodynamics.
https://www.dieselnet.com/standards/cycles/hwfet.php
How fast does traffic cruise on the highway where you are talking about?
Even a Tesla Model S isn't going to have it's stated 265 mile range if your cruising at 80 mph (closer to 225 miles).