Thought of doing it. I heard something about the possibility that Mobil has gone to different base lubes in their North American offerings, save their 0W-40. I also tend to go a bit longer than severe intervals along with most short trip driving in cold temps.
I live in the San Francisco Bay Area, although I may go into the mountains. I don't know if this interval is going to extend into the winter months when I might visit Lake Tahoe or Yosemite.
I figure this should be OK. I hear Subaru uses 5W-40 oils in the UK for the same engines.