UPDATE!! I GOT IT!!!

Yesterday I got to 730 miles! I had another 30-40 miles leftover but I was on a Toll Road and the next gas was around 30 miles, didn't want to push it and I had forgotten my gas can

Final Mileage was 51.4mpg, but that included the last 100 miles driving at 65-75mph. By the way, I was able to draft a semi during that time and average 48.8mpg for those 100 miles, going 65-70!!

7 - 600-mile tanks... farthest on "normal" gas fill= 643miles

And ONE 735-miler!! (cheated, over-filled tank )