My Best was 401 Miles on 12.6 Gallons across Oregon up the Interstate 5. I kept it at 60-70MPH and no AC or windows down with bald tires
This was not fun but I had to see what the best I could do was.
The rest of the trip from LA to Vancouver was:
270Miles =10.7 Gal (Southern Cali)
368Miles =12.6 Gal
379Miles =13 Gal
401Miles =12.6 Gal
119Miles = 4Gal
Around town I only get about 240Miles. We have lots of hills.
My Gas gauge is on empty around 13 Gal.