Just a little tidbit... After 10.2k km (6.4k mi.)....computer said 'next oil change at 13.1k km (8.2k mi.)....no doubt oil was BMW Synthetic (made by Castrol)...level was down slightly, oil was caramel brown...not too dark, but there was some brown stain developing on the inside of the filler cap (as I had when I used this oil) and this was after on 6.5k mi. on a new engine! Conveniently, the engineers now make the intake as filler area black plastic as to completely disguise what's going on under the cap (the area immediately under where the oil is being poured). My take: group III's...better performance than group II...can be used for extended intervals, but definately NOT as good as PAO group IV for soot control during this exteded drain interval over long term (beyond the warranty)...Period.