Well i put 11.894 gallons in my quantum the other day and still had somewhere between 1/8 and 1/4 of a tank left.
Also if you have a Bently it sould state in there or even the owners manual.
Aw614... Thanks. I took a road trip, and averaged 33-34 mpg. I drove about 325 miles before I filled it up. Still don't know the real capacity, so I just carry a gallon of gas in case I should run out. Still need that sending unit!! David.