my 1997 328 has done the same thing for the last two years, and yes I have checked it has oil in it. I went on another website and the consensus of opinion there, was that it was a faulty warning light or some such !Removed!. Anyway, apparently it's quite common. I'm sure a quick Google search or look on a 46 fanatics will confirm this information. As I am a cheapskate and well-known for my propensity to spend it not a penny unless I have to, I will continue watching the yellow light. Yes it is annoying, can be worrying, but as I said my car has been doing it for two years and it still drives perfectly well. Best wishes