Thanks for the replys. They all make sense. When I gas up, usually just a little above the empty mark, the car takes about 10 gallens. So it looks like I've got about a half of a tank to go before my light comes on or I run out. I just don't like running below E. My Dad always told me that 'You're never lost if you have at least a half of a tank of gas.'
The wife doesn't think too much of this philosophy though.