BMW builds the cars and therefore provides the best recommendations. Your car will run fine and dandy with BMW's oil change intervals, assuming you drive 12,000 - 15,000 miles per year (remember that oil gets dirty AND old). The car will tell you when it is time to change your oil.
If I had a service schedule for every 15,000 miles per oil change, I would be changing my oil and filter on my own time every 4,000 miles (even with synthetic oil), but I think this just helps us all sleep better at night and nothing more.
If I had a service schedule for every 15,000 miles per oil change, I would be changing my oil and filter on my own time every 4,000 miles (even with synthetic oil), but I think this just helps us all sleep better at night and nothing more.