I'll be changing the oil on my 135i every 3,000 miles, same as I did on my Exige. I'd rather "waste" money on synthetic than risk big time repair costs.
I have no doubt that following BMWs scheduled maintenance plan will keep my car running up to 50,000 miles or for 4 years.
For all of you BMW huggers believing that 15,000 mile oil changes are healthy: did you ever hear about the decission to reduce the number of olives in martinis served in first class that saved $40,000 a year?
Use your own intuition and your own scientific data instead of being a blind believer.
If it tests like burned oil, and it smells like burned oil, IT'S BURNED OIL!
+100 to op!
And btw: changing your oil and your filter doesn't cost much more than a tank or two of premium gas.