Looks like somebody has been
Looks like somebody has been doing too much drugs. Hey Carey, turn the keyboard around - right side up. I think you are typing on an upside down keyboard!!!
How full or empty the tank
How full or empty the tank is, does not seem to affect the shrinkage of the tank in winter.
You should however, NEVER go below the last two bars. That's when the tank can run dry without warning.
I just keep track of the consumption display. If I am averaging 53mpg, and have traveled 300 miles since fillup, I figure I've used about 6 gallons.
For me, at least, the consumption display seems to be EXTREMELY accurate. I can predict +/- half gallon, how much fuel the tank will take at the gas station.
Only exception is if the temperature changes suddenly, then the tank capacity increases or decreases, and I put in a couple extra gallons on fillup, or a couple gallons short.
And that tells me if my tank is at full summer capacity (12 gal) or shrinking down to it's winter (8 gal) capacity.