Cammy,
Actually the correct mileage is 170 x 2 + 120 = 460 miles NOT 510 (that's the mileage to KING, NC to match witness statement)
460 Miles @ 19 EPA EST MPG HWY = 24.2 gallons of gas need. JY's SUV held 22.5 gallons
EPA Link: http://www.fueleconomy.gov/feg/noframes/20416.shtml
Thank you, Shadow.

I was including the mileage from Birchleaf to Hillsville, and then Hillsville to Birchleaf and then Birchleaf back to Hillsville when talking about all the things that could have happened.
Besides the obvious one of running out of gas.