First the issue....
While I was on a long trip on the interstates, and selected gas, it gave me a bunch that were 0 min off my route, but it was at the very end of the trip after my exit on the interstate, which was over 300 miles away. My car said I had only 40 miles of travel left on this tank.

The idea is that when you hit find gas while navigating, it should bring up a scroll list or buttons giving you choices for how many miles you need it in. 4 or 5 choices would be adequate. It could be 1, within 5 miles, 2. within 20 miles, 3. within 50 miles, or 4. Greater than 50 miles/no limit.

Then the app could search for the gas options with the minimum off the route within the miles constraint entered by the user.