Originally Posted by whyireef

I'm an avid engine professional. I've driven VW turbo-diesels for many years. In my VWs, I use Euro Elf seventh generation full synthetic and do the changes myself (even under warranty, I perform all maint/repairs myself) and I perform a 30 pt oil analysis via Caterpillar engineering after roughly 15,000 mls on each change and always completely change via extraction at 20k mls. I've logged more than 600,000 miles on 2 of these little VW diesels using synthetics. My current '05 now has 160k mls and runs better than the day it was new (compression wise).

So - my new X5 35d has 1,600 mls on it now and I don't plan on changing the oil earlier than the factory intervals. The Castrol synthetic BMW is using will easily go beyond 15k mls.

Lastly, myself and many colleagues have performed oil analysis on engines changed at 3k, 5k, 10k, and 20k mls. What we've found is early changes promote metal wear and other early engine wear (sounds counter to logic, but there really is a science behind it). I wouldn't change the oil in my X5 35d early if you paid me.