Does anyone know what the line at the end of the gas gauge under the nav screen means. I've just recently noticed that it is not always illuminated. Just for clarification I'm talking about the thin line to the right of the gas gauge on my 05' cooper S with navigation.

 

HA! I'm an idiot! The line and the gas pump symbol come on when the head lights are on. Jeez, I feel really dumb!

 

I remember when I first noticed the line you are talking about and thought my nav screen was messed up. As you discovered, the line shows up when you turn on the headlights and serves to mark the far end of the gauge which would otherwise not be able to be seen at night.