along your way, this is the web calculator you need?
Most of you know about Gasbuddy for gas prices in your area, but did you also know about their Trip Calculator?
A link that would be worth while to put on your favorites for use the day before you leave on a trip. GasBuddy Trip Calculator
It's your typical mapping program with two nice functions. The first is, it will inform you of the best places along your way to stop for fuel with the best price. The other function is when you hit the "View Map" tab you can move along your route to see gas prices from start to finish.
The nice thing about this interactive map option is you will be able to see where you can top off with the cheap stuff before hitting a high fuel cost area.
Let me add a tip to save you some grief, when you input your start and finish points make sure you put in the whole address. Street number, street, city, state, zip code. Otherwise it will give you an error message.