Q:

Car stored for 6 months shows low oil level after 300 miles

Just bought a car from a BMW dealer and the guy told me it was sitting for almost 6 months before I came to purchase it. When I left the dealership the oil was above the min mark showing green. Drove the car for 250 miles and the oil was at the min marker. When I started the engine this morning the oil level was yellow. I have added 1L of oil right away and it was still yellow then I added another one. Right now it is almost at max and I drove it for about 20 miles without any loss in level. 
Can this be from the car being parked for this much or I should expect a low level tomorrow when I start it again?
Engine is a 3000cc diesel/2013 X6 M50d

A:

The oil level is not going to decrease due to it sitting for six months unless a seal went bad. It would appear to me you have an oil leak somewhere. This doesn't mean you are going to have low oil tomorrow morning, but it does indicate you need to keep an eye on the oil situation. 
What you can do is to check the ground where you normally park your vehicle and see if you can spot any leakage (spots) on the ground. If you don't, put a large piece of clean card board (corrugated) under the vehicle over night under the engine. You'll want it to totally cover the area where the engine would be at. In the morning pull it out from under the vehicle and see if there are any spots and notice if you can tell what part of the engine the drops are coming from. This might indicate where the oil is coming from. Then you can check that part of the engine to see if you can pinpoint where the leak is occurring. 

A:

It could be that the oil level was low before it went into storage.
Upon sitting, the oil will have settled  for a few % above low error.
When driving the oil becomes distributed around moving parts and resulting in low oil alert.
If the oil level drops again now you have added more oil, then suspect leak. If not, its just a very wierd coincidence.

