[attila]

Here is the story: I track the car relatively often (4 track days in May only one in June but 4 coming up in July)
So I like to change the engine oil more often than BMW recommends. After the 1,200 mile service I changed it at 4,200 miles and now at 8,000 miles I went in for another oil change. And here is the thing, the SA was telling me that based upon the "key reading" my car needs an oil change (just after 4000miles), so they did it free of charge?? I am not complaining but somehow worried that the oil could have been deteriorated so much that the car needed a change?!!
What is the car actually measuring in the oil? How is it determined by the ECU that the car needs an oil change? By the way no service light came on, nothing was indicating that something maybe not right.
Thanks