| I've used 'em all. As for fully synthetics, I'd recomend Royal Purple, RedLine or Mobil 1. While most people would cringe at the idea, i once went 17K in between changes w/ Redline and when emptied, the consistency was unchanged. No breakdown. I've had similar results w/ Royal Purple. BMW recomends Mobil1 5W30 or Castrol Syntec 5w30.
Personally, i think more importantly than using one of the aforementioned, is the need to be consistent w/ useage. My current whip has been fed Mobil 1 5w30 since day 1, so intend to keep it that way. Cars most certainly get acustomed to the oil it's fed, frequent changes in brand and weight are bad ideas. Contrary to popular belief, there's really no need in changing weights based on season/temperature, unless you live in a climate that has dramatic changes in season.
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