HowMuchGas app calculates gas cost for your trips! You can enter starting and destination address and see the result on the map (google maps) along with details such as cost, distance and trip duration. View a demo in youtube! http://www.youtube.com/user/SQLearnMobile
For more precise results you can select your car (using data from the fueleconomy.gov website for over 60 makers) and where you are going to drive (city, highway or combined). You can even type in your car's gas mileage using "My mpg" feature!

Features:
•Detect your location as starting address

•Use waypoint

•Select your vehicle from a large database of US market models or
•Insert your car's gas mileage using "My mpg" feature

•Insert your own gas price ($/gallon)

•Select type of driving (cty, hwy, cmb)
•Avoid tolls or highways

Results that contain:
•Distance and estimated time

•Cost for one way trip, round trip or working week

•See your route on the map (google maps)

Requirements: iOS 3.1.2 or better, EDGE, 3G or WiFi connection