No pissing contest here. I'm coming to the table not knowing much at all about oil and quickly finding that I've been doing the wrong thing here using Castrol Syntec 5W-30. I did some research, looked at the BMWUSA site and I think I'm pretty much sold on using Mobil 1 0W-40 at this point. It's on the list of approved oil to use by BMW, is rated as a Group IV oil, and Autozone is running a deal on it right now
I would use the BMW Synthetic, but this looks to perform just as well and is a little bit cheaper (maybe .50 a quart) and more convenient to get for me at least.
I wasn't assuming that a different weight oil would last longer, it just seems odd that the BMW Synthetic oil is one weight and that all of the other approved oils are another weight. I have no idea why that is. I just mispoke....I'm the last one to make any claims