This is the first time I am hearing this, as far as I can tell if I were to block the radiator which I have tried as a test of my Nisaan, the temperature goes up accordingly and even on test benches, both MB and Nissan temp gauges exhibit the same specs, in a tub of hot liquid, the temp reading is same for both the MB as well as the Nissan. Why would the Japanese joepardize their engine with a thing like this.

The fact of the matter is that unlike MB and other Euro cars which are specificaly designed to run in cooler Euro weather, Japanaese cars have much superior cooling systems and in general tend to run much cooler. I have taken both the vehicles as well as my friend's G-Wagen with OM 617 turbo engine to the desert in Rajasthan and can tell you that between the three, only the Nissan help up its poise at 56c ambient outside temp. Gotta give the Devil its earned due in this case.