I am in Michigan (on the west side) and have been averaging about 33 mpg in this cold weather. I am trying to avoid going out at all if I can avoid it. The weather over here is really bad.

Did you run the car well past the point that it tells you that you have zero miles of cruising range left? If not, I would strongly doubt the 17.7 gallon value. You would have to run the tank bone dry and then fill the entire filler neck to be able to put that much fuel in.