I just checked what the site recommends for both of my cars, and all recommendations are on the heavy side, particularly for the Outback. The Owner's Manual for the Outback calls for 0W-20, and the website is recommending a 15W-40 for all seasons, with the lightest recommendation being a 0W-40 for winter use.
For the Mercedes, it the recommendations are a little on the heavy side. Mercedes recommends 5W-30, 0W-40, and 5W-40. The site is recommending several XW-40 oils, but mostly with winter grades heavier than what Mercedes recommends. I don't think this is a difference between European and NA recommendations, as from what I have researched, Mercedes makes the same recommendations for both continents.
Interestingly, except for one winter grade oil, the site is recommending the very same viscosities for both cars. I also noted that the site does not make separate recommendations by engine. It only narrows it down to model.