It sound like one of our trips but we usually only travel about 250 to 300 miles a day.
At an averages speed of 50 mph that is 5 to 6 hours behind the wheel. Of course we never pass up a tourist trap or other road side attraction, which adds to our daily travel time. A stop at Zion, Bryce Canyon, Custer State Park, Mt. Rushmore, Pictured Rocks, the Arch and a host of great Western museums can easily require a half day or more each to visit.
At 60 mph we get 10 mpg with no wind but our adventures often take us far from the Interstates.
So, good luck and let us know how your trip went.