Total mile per full tank?

07, DC, auto, 4X4. I'm looking for a gas station at around 300 miles city or hwy. I've gone 350-360 a couple of times on road trips, but I start looking for a pump at 300. The times I pushed it to 350+ is when in metropolitan areas with a pump every 3-5 miles. On rural roads I won't push it past 300 miles. With normal commuting I'm running pretty low at 300 miles.

I usually get right at 19.5-20 mpg hwy. I've been in some headwinds that cut me to 16-17, and caught mountain roads where I could coast for miles where I've gotten as much as 23 on a tank. Normal commuting I'm almost exactly 17 every time.