As we talked about the other day, *I'm* the one that is more likely to get my gas tank down pretty far before filling. My wife is paranoid about running out of gas, so she's probably not often filling up with less than ~15-20 miles to empty reported by the car.
But for the most part, we don't drive each other's cars very often, and when we go out together I drive 95%+ of the time, and I prefer to do it in my Flex. So I rarely ride in her car and thus never really stress about her gas level.