Hi Vanessa Anderson,
I have it from a very good source from someone who has worked for GM for many years and is very experienced with auto servicing.
They told me to keep a minimum of 1/8 of a tank of gasoline in your car, and 1/4 tank would be better.
Contaminants can accumulate in your gas tank and therefore get sucked into your engine should the level get too low.
Moisture can also develop and will freeze in extreme cold weather. This I know for a fact.
Cold winter night while driving up a steep hillside, we actually heard a chunk dislodge and slide inside the gas tank as we traveled upward. The frozen mass slid into a position and choked off any fuel and seconds later, the car's engine just stopped 3/4 of the way up the hill.
There was not much gas in the car when we started out, and we thought that our drive home was short enough to make it on the gas that we had. While the car was parked for a few hours, the water in the gas froze and the change in our upward travel caused the iceberg to shift.
Since then, we always keep at least 1/4 tank of gas in all of our vehicles.
Hope this helps.
N T T