I usually fill my tank when its half full
in the winter should I get a 1/2 tank of gas or fill it up when half full on 2000 Saturn LS1
Keep it full so you don't get a lot of moisture/water in the tank as that can lead to other problems.
1 more answer
Always keep tank at least 1/2 full to advoid sucking up sediment off the bottom of the tank.