So about 15-20 miles? With only 6 or so highway you've got your work cut out for you! Try to get into 5th by popping over 43mph, and hold it in 5th. 4th will kill mpg. You should be able to hold 5th all the way down to 36-37mph.

Coast coast coast- use neutral a lot, or keep it in gear for a 'light braking.'

Good luck! I'd love to hear about a NYC driver who gets >30mpg on multiple tanks.