36 is about right for highway cruising (at a reasonable speed) on mostly flat ground like the east coast. Mostly it’s dependent on speed and lack of hills to climb. Both kill fuel economy.
I’ve got a 6,000lb Jeep Wrangler that will do 21-22mpg all day long at 60mph on a flat highway like I-95. But if I move the speed up to 70-75, or I’m driving someplace hilly like I-81/I-64, the mileage plummets into the high-teens.