DMens,
I have exactly the same problem as your car, also a 523i. Only difference mine is still under warranty. Like you I never got a satisfactory answer from AB re the problem, always some rubbish about engine oil used being too thin and that the problem shud go away with time and mileage. Instead my problem got worse over time! Now at barely 30k, if I'm not wrong, have topped up at least 5x already.
Actually they did some test on my car late last year and told me to come back 1k later for them to measure the amount of oil consumed. But of course everything seemed fine at that mileage. Less than another 2k later the light came on, asking to top up 1 litre. And they just did that without telling me the result of the earlier test. I got fed up and contacted BMW directly. So they arranged for another test for me in Mar but like before, never came back to me with the result. Meanwhile engine oil kept disappearing! So I contacted BMW directly again and had to send in my car to AB again last week. This time they admitted that there was something wrong and my engine block (not whole engine) need to be replaced!
As of now, I'm still waiting for them to call me when the necessary parts arrive. And yes, do insist on a courtesy car when you send yours in for the same replacement. Seems it's going to take them 7-9 days to do it, meaning a good 2 weeks including weekends!
We should exchange notes, man.
BTW forummers, wouldn't a change of engine (requiring change of engine no) affect my resale value or make it difficult for me to sell the car next time?
Cheers
Pete