4. Mercedes-Benz G550
It’s boxy, mean-looking and can tackle tough off-road conditions with the best of them. But the G550 is based on an antiquated if not capable design that is not engineered for fuel efficiency. That’s why the truck achieves an EPA estimated 12 mpg in the city and 15 mpg on the highway, which adds quite a bit of cost to owning the luxury SUV.