I've noticed that when the tank is down to 1/4 capacity or less, the fuel gauge will occasionally go down a bar, then back up again. Yesterday it went from 2 bars to 1 (triggering the low-fuel light) for a couple of minutes, then returned to 2 bars (light went out). I was on my way to the gas station anyway, so I wasn't too concerned.

Something even more interesting happened a couple of weeks ago on my way home from work. The gauge dropped to 1 bar (triggering the light), then about 20 miles later the last bar disappeared. Since I was only ~15 miles from home, I decided to do an experiment. I pulled into the nearest station and put in exactly 1/2 gallon. About a mile after hitting the road again, the gauge suddenly popped all the way up to 2 bars! (Next day I refilled the rest of the way at a nearby station where the price was 7 cents less.)

Has any other '05 HCH driver encountered this or any other kind of strange behavior on the fuel gauge? Is the mechanism used to estimate remaining fuel simply unreliable at low levels?