Just took a 800 mile road trip with my 2015 Outback. It had 24K miles on it with a Thule Atlantic roof cargo box. Mostly highway driving 75 to 78 mph with cruise engaged, temps around 35 degrees thru OH & IN. Averaged 22 going and 18.5 coming home against a stiff oncoming wind. I'm hoping without the cargo box I can get closer to a 30 mpg average. I thought the Outback would be a lot better than my old Chevy Tahoe that I owned for 20 years and got 16.5 mpg average for it's entire life.