The Mobil 1, 0w-40 consistently shows significantly higher valvetrain wear (Fe) than other competitively priced synthetics, including , Redline, Delvac 1, Royal Purple and the GC/0w-30. It consistently shears down by 10%-12% after 5000 miles of use in the VW/Audi, SAAB or Subaru turbo engines. It shows NO advantage over the very shear stable, Mobil 1, 10w-30 in any application I've seen to date - either in terms of wear protection or TBN retention.
There is no test data in any of the SAE, "Fuels & Lubricants" papers published in the past seven years that shows the 0w-40 outperforms the Mobil 1, 5w-30 or 10w-30 - except in terms of "staying in grade". Since this "stay in grade" performance is achieved by shearing significantly and then thickening back up due to oxidation/evaporation, I don't see that it offers any tangible benefits to the end user.
These are facts which are clearly and consistently supported by the past three years worth of UOA data on this site - they are NOT opinions....
Any experienced engineer who looked at this same data would come to the same conclusions....