shallals

Hi Everyone, I am a new and proud BMW owner and am already loving this forum. Would just like to ask one question. I have a 2007 530i and the alert popped up on my idrive stating that I must "Add" engine oil as it is at its minimum. Does that mean I need to go for a full on oil change or do I just top up the engine oil? Also, where would be a place I could purchase this engine oil to top it up myself? Thanks in advance fellas!