As long as your driving was on the highway, I don't see any reason why you wouldn't be able to eek out 500 miles (except for the guy who said he gets 270 - I think you need a major tuneup dude). Just make sure there's a gas station at mile #501. And don't do this too often - the fuel pump's not gonna like sucking all that crap off the bottom of your tank. That's why I always refill when I get to a half tank.
my best MPT = 452.6
related:
best MPG = 45.51 (during cross country trip traveling between 45 and 55 mph)
most gallons filled: 13.437
each of these were on separate occasions.
45.51 mpg! Sorry man, I'm not buying it.