You'll need to specify the engine to get a more accurate estimate. However, expect a range generally like this:
* V6: Around 18-22 mpg city and 25-28 mpg highway.
* V8: Around 15-18 mpg city and 22-25 mpg highway.
These are estimates, and actual mileage will depend on driving style, road conditions, and vehicle maintenance. The best source for the exact fuel economy figures for a specific 2007 Ford Mustang would be the owner's manual or the EPA's FuelEconomy.gov website.