Car gas tank capacities vary widely, based on the size of the car and the manufacturer's expected fuel efficiency. A sub-compact car has a tank designed to hold 8.7 gallons, while a full-sized sedan can hold as much as 23.8 gallons of gas.
The owner's manual contains information on a car's gas tank capacity, and the manufacturer's anticipated fuel efficiency. If the owner's manual is not available, a driver can find the information on most types of cars by performing an Internet search to bring up a specification sheet for the vehicle in question.
Most modern vehicles are designed to drive approximately 300 miles per tank of gas. Early vehicles, such as the Model A with an 11-gallon gas tank, had gas tanks designed to fit the available space in the car's design.