I have 3 BMW. 1996 BMW 1.9 Z3 106k miles (the wife's). 1996 BMW 328i 257k
miles. 2000 BMW 540i Sport 73K mile.
I've used what ever quality oil (non synthetic) is on sale at Costo on all
the cars (540i new addition) and as you can see from the 328i I get lots of
millage out of my cars without any oil related problems.
So what's the advantage of using synthetic if I can get 250k miles (328i
still runs great)? I adhere to the belief that changing oil more frequently
than manufactures recommendations is a good idea. Dirty oil is dirty oil, so
changing more often is best practice.