So the question here is...how often do you fill up your tank? I only fill up once a week...which leaves me an overage...and that is on a ~300 mile week. If you figure the 650 mile they claim, I wouldn't have to fill up for 2 weeks. That leaves me 2.5 tanks in storage every time I fill up. End of the month I have enough for 5 more tanks...I can turn off my generator for 2.5 months.
Did you count the number of tanks in each of the cars?