You can tell when you are about to run out of gas by watching test six. The right side will stick at 014 or so until both tanks are depleted. Once that starts to drop you have about 3.6L of gas and can go maybe 10 miles before a walk with a gas can is in your future.

__________________
2011 E70 • N55 (me)
2012 E70 • N63 (wife)