* The owner's manual: This is the most reliable source.
* The fuel filler door: The sticker on the inside of the fuel filler door sometimes lists the fuel tank capacity.
* The vehicle's specifications: You can often find this information online using the vehicle's VIN number or by searching for the specific model and year (e.g., "1994 Ford Explorer Sport fuel tank capacity").
Expect the tank size to be in the range of 19-21 gallons, but confirming through one of the above methods is essential.