Happy Friday to you, too, sir.
I see we read the same boards. That's good! WRT bobistheoilguy.com (BITOG), several months ago, Shannow, a retired oil industry scientist (with whom I assume you, too, are familiar) pointed out that the sources claiming a 2% improvement in 0W-16 motor oil over "other weight oils" were advertisements made the Japanese companies themselves. In other words, there has been no independent corroboration of those claims. In this regard, as I noted above, neither XOM nor TM have stated, or even suggested, that fuel mileage improvements of "up to" 2% might be possible, and I don't doubt for a moment that they would do so if they could.
Also -- and most significantly -- the two sources most often quoted (one of which you linked) speak only of the potential improvement in fuel mileage. You have to read the "fine print" (so to speak) to see that the 0W-16 weight oils tested were compared to conventional 5W-30
weight oils. That, too, is significant. In other words, a 2% improvement isn't at all meaningful when you realize that a 5W-30 weight oil is roughly 12% more viscus than a 0W-20 weight and 19% thicker than a 0W-16 weight oil. At least half the claimed fuel mileage improvement can be found in these facts alone.
Finally, as Shannow pointed out, the company that reported the 2% gain -- JXTG Nippon Oil & Energy -- footnoted their announcement with this statement:
"1: [Results] Based on our internal test data of the Japanese Fuel Saving Test (JC08 Test at Cold Mode). It is not guaranteed under any driving conditions."
In summary, Toyota's goal in prescribing 0W-16 weight motor oil (among other fuel economy measures) is to increase the company's overall fleet MPG average
. The FE improvement per car may be only 0.2-0.8%-- numbers I think are ballpark -- but the cumulative fleet average
is huge. And, as you may know, TM is allowed to sell those energy credits to other manufacturers to enable them to meet U.S. federal FE guidelines. It's been a while since I checked, but the last time I looked, TM was earning tens of millions a year selling fuel energy credits to other manufacturers such as BMW and MB. It's a major source of TM's annual net profit. That's the principle reason that why TM wants you to use 0W-16. Thankfully, it's also a very good product.