I did not want to do all the research but below is a post that helped me tie in the ACEA and BMW LL (long life) spec.
I did some spell-check and don't know validity but it seems to consistent with other things I've studied.
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http://bimmer.tribe.net/thread/cf7e78ff-0840-46cd-af6a-d7c8ab637182
Re: Type of oil
Fri, March 3, 2006 - 9:34 AM
"I'm going to chime in here as a long time oil enthusiest that has spent way to much time on the subject. If you really want to get into it, go spend some time on bobistheoilguy.com and you will get a whole plethera of knowledge.
What to look for in a BMW oil:
1) BMW has its own oil specs. They are BMW Long Life (LL). There have been three standards LL-98, LL-01, and LL-04. BMW LL-98 allows for Group III hydrocracked oils, but LL-01 is stricter and only allows for Group IV or Group V based oils. LL-04 is very new, designed for primarily diesels in Europe and no oils sold in the US actually are LL-04 approved (Amsoil doesn't count as they claim their oil meets the standard, but it isn't approved).
2) The proper oil for all climates is oil that meets BMW LL-01 or better. There are only three oils that actually meet this spec widely available in the US. Mobil 1 0w-40, Valvoline 5w-40 Synpower, and Castrol 0w-30 (you have to be careful with the Castrol, there are two versions out there, the one you want will say on the back in little writing that it is made in Germany, and will specifically list the BMW spec, Mercedes 229.3 & 229.5 and ACEA A3).
3) All BMW Long Life oils are ACEA A3 oils. An ACEA A3 oil means that it has a high temp high shear (HTHS @ 150c) of more than 3.5. Note that A3 is mutually exclusive of ACEA A1 & A5. A1 & A5 oils have an HTHS of less than 3.5. A5 is simply a newer and stricter standard of A1, so if an oil is A5 rated than it is also A1 rated. NOT ALL A3 OILS ARE BMW LL OILS, ONLY THOSE SPECIFICALLY LABLED AS SUCH.
4) Mobil 1 30 weight oils are not A3 or LL approved. So the next question that will be asked is why does BMW USA recommend them? It is because they never have updated their recommendation from the 90's when Mobil 1 was available in the US in either 30 or 50 weight. There was no 0w-40 then. THE ONLY MOBIL 1 OIL THAT IS BMW LL APPROVED IS THE 0W-40.
5) Don't get too hung up on weight. 30 weight oil runs from about 9.5-12.5 cst at 100c. Mobil 1 30 weights are formulated on the light end of the 30 weight scale at about 10.5 cst, so are nearly 20 weight. By contrast BMW's relabeled Castrol 30 weight is about 12.2 cst, which is nearly a 40 weight. As a rule of thumb, Mobil formulates on the light end of any grade, Amsoil on the heavy end.
6) Redline is a great race oil. For street use it does not work well for extended intervals. The problem is that their chemistry is very old and the oil tends to oxidate quickly and generate higher wear number than Mobil 1 or Amsoil when used in street vehicles.
7) The best widely available oils for your BMW. 1) Mobil 1 0w-40, 2) BMW 5w30 synth. Why the Group III BMW oil when it is only LL-98 approved instead of the better LL-01? It is because the 15k interval used by BMW is too far for even Mobil 1 oils under most conditions, so either oil should be changed at 10k or less intervals. As it is easiest to just change once between the indicator lights (about 7.5k miles) the advantage that Group IV oils have over the BMW labeled oils are largely negated.
8) You want Mobil 1 0w-40 but can’t find it. Mobil 1 5w-40 Truck and SUV will work fine. Note it is not not BMW LL approved or ACEA A3 rated, but meets the spec with an HTHS of 4.1.
To answer the specific questions of the poster. The Amsoil 0w-30 is a good oil BUT DOES NOT MEET ACEA A3 OR BMW LL-01 SPECS. The Amsoil that claims it meets BMW LL-01 and ACEA A3 is the 5w-40 (note they don't have the approvals, likely because of the cost of obtaining them). There is no point in running Mobil 1 15w-50, all it will do is give you lower gas mileage and no real increase in protection. Also, the BMW Vanos system doesn't like 50 weight oils. I ran 15w-50 for years in my wifes M50 motor 525i and then switched to 0w-40. I found the car had less startup noise, got about 1mpg more on average, and oil consumption dropped from 1 quart every 1500 miles to 1 quart every 4-5000 miles."
