Dear all, how are you doing?

Just a quick question. We have a old mercedes 300E which we lost the
user's manual long time ago. The car has extremely low mileage and was
in good condition until recently when the engine got started, there is
a indicator will continue to but lighted up and won't automatically
turn off. I can't remember what this indicator really mean, could
anyone help? A image is available at here:

http://aycu20.webshots.com/image/19539/2002044021537460153_rs.jpg

We also noticed that some kind of oil is leaking as the car will leave
some oil stain on the garage floor, is this related to the indicator?

Thanks for your help!