Twice now it has said I have 100 miles remaining only to hit 0 remaining after between 60 and 70 miles of driving. The obvious cause would be a decline in fuel efficiency, except there isn't one. In fact, last night I drove to maximize fuel efficiency for the 65 miles between starting the car and refueling, I was at 49 mpg average (per the cars calculation) . Normally on my commute I'm hitting around 41 mpg average, so if anything the 100 miles remaining estimate should of been conservative relative to typical fuel consumption rates.

After refueling the miles remaining went up to 550. This is within the normal range for a full tank.

Does anyone have any idea what may be causing this problem?