This is a very interesting subject. I did my oil change last December and when I emptied, I got 9 litres of oil. When I think back, at least 2-3 weeks after the oil change at the dealership, I got a warning to top up the engine with a litre of oil. Anyway, after my own oil change and two weeks later, I got a warning to top up with a litre of oil. Instead, I topped up with 800 ml. The idrive level indicated all fine and I haven't had to top up since. So does it mean when it ask for a litre you top it up with less. I only did this because I got 9 litres when I emptied. So it could be that the dealerships are automatically putting 9 litres of oil.