* 26 gallons: This was the most common size.
* 31 gallons: Some models, likely those with extended wheelbases (EB), had a larger 31-gallon tank.
To know for certain the size of the tank in *your* specific 2002 Ford Expedition, you should check:
* Your owner's manual: This is the most reliable source.
* The fuel door: The sticker on the fuel door sometimes indicates the tank capacity.
* Your vehicle's identification number (VIN): A dealer or online VIN decoder might be able to provide this information.