To find the exact gas mileage for *your* 2007 Chevy Cobalt, you should check:
* Your owner's manual: This will have the most accurate figures for your specific vehicle configuration.
* The EPA's FuelEconomy.gov website: Search for the 2007 Chevy Cobalt and select the engine and transmission type that matches your car. This site provides city and highway MPG estimates.
Without knowing the specific engine and transmission, I cannot provide a precise gas mileage figure.