Originally Posted by andrewwynn

Prob the rate of consumption you fill up too often never gets that low. That said anybody with e53 had better pull up test six and drive down to single digits to empty and confirm their transfer pump is working at least once a year (until they rebuild their transfer pump). When monitoring test six the right side should stay at about 1.4L until the left side gets to zero. If the right side starts to drop when there is ≈ 20L left the transfer pump is failing and it's time to rebuild it.