I think you're missing my point. Mobil had to begin with base oils and additives to create an oil to meet the specs. Looking at the VOAs, all grades of Mobil 1 seem to be essentially identical as far as additives go.
I'm not so sure. I think all grades of Mobil 1 use the same three basic base stocks, but in different proportions. I honestly think the HT/HS of the 0w40 is the deciding factor in meeting those OEM requirements. Disregarding that, I think any grade of Mobil 1 could go the distance with the 0w40. 3MP's test of the 5w30 is bearing that out.
I don't think GF-3 means squat to the European OEMs, since it's strictly a US spec/rating. There are only 6 oils currently made that meet 229.5, and Mobil 1 0w40 is the only one with the GF-3 rating. Keep in mind that A5 is the ACEA "fuel efficiency" rating.
Exactly!! First, let's look at the summary wording for the MB 229.5 spec, "...for passenger cars with gas and diesel engines with extended drain intervals beyond 229.3 oils, to 30,000 km, min 1.8% fuel saving..." Now, look at these other oils you've listed. They're all 5W-30s! Are they also all A5-rated? What are their HT/HS numbers?
I have to assume that you mean 229.3 & 229.5 are "the toughest European OEM extended drain specs" (since you haven't identified any others). If 229.3 & 229.5 both use ACEA A3 as a baseline (where can I get a copy of these MB specs?), & require 1% & 1.8% fuel economy increases (respectively) over 229.1 oils (typically 40wt oils; am I reading this correctly?), then the MB specs answer your question for you. All the other M1 oils either don't meet the A3 base requirement or don't meet the fuel economy improvement requirement. Which brings us back to my original comment, "... it's a combination of both the more protective HT/HS rating & the energy-saving GF-3 rating. ..." (Whether or not Euro OEMs care about GF-3 is irrelevant, because the results are the same.)
With the exception of Mobil 1 15w50, the other grades of Mobil 1 don't meet A3; they are A5.
Yes, I agree; I've also already said this.
Yes, I agree (both statements). It's possible that the other five oils on your list also meet GF-3, but since they're not globally marketed, there's probably little reason for the manufacturers to got to the trouble & expense of having them certified.
I never made this assumption; I'm sorry if my statements aren't as clear as they should be. The fact that it meets 229.5 means that it meets the fuel economy requirements of 229.5. The fact that it meets GF-3 means that it meets the fuel economy requirements of GF-3. Since I don't have the MB specs, I wasn't originally aware there were fuel economy requirements in them.
My point was simply this: Mobil 1 0w40 meets all the toughest European OEM oil requirements, yet the additive package is pretty much identical to the other grades of Mobil 1 for sale in the U.S. Therefore, my original question: "What's so special about the 0w40?" as in "What is it about the 0w40 that makes it capable of meeting the extended drain requirements of European OEMs where (presumably) the other grades of Mobil 1 can't?" The only distinguishing feature of 0w40 is its higher HT/HS numbers and the A3 rating (disregarding the 15w50). Therefore, my answer to my own question is the A3 rating is what makes the 0w40 "so special." Apart from that, ANY grade of Mobil 1 can "go the distance" with the 0w40.
Maybe, maybe not. Castrol introduced the SLX in 99, and it was on the cutting edge then. As I have speculated, and MolaKule has confirmed, the base oil make up of the SLX has to be predominately esters. The additive chemistry as revealed in my VOA is rather ordinary, but because of the base oil, it doesn't have to be otherwise.
