Please read Mercedes, Volkswagen and other European manuals for oil requirements, Note the specs, and compare with what is on the average oil can from a no-name supermarket oil.
Mobil 1 is a good synthetic, but the stuff sold in most US locations does not meet VW requirements, for instance. Mobil makes two synthetics for that reason, but THEY ALL COME OUT OF THE SAME FACTORY! Making a high quality oil is a matter of selecting the best base stock and adding the needed additives to meet the manufacturer’s specs.
For heavy duty diesels and gas powered engines, each manufacturer, such as Mack, Cummins, Caterpiller, have their own spec for oil. Shell sells a number of engine oils in North America. They specify whether these oils meet the US (API), ILSAC GF-3 (Euro), ILSAC GFF-4 (Euro), or JASO T903 (Japanese) specifications. Their best oils met all these, but the no-name brands on the Walmart shelf will likely NOT, and only meet the US standard barely.
Any oil company distribution depot will gladly give you a copy of their lubricants and application booklet. It makes for very interesting reading.
In the future will likely see a convergence of lubricant specs.
Years ago, oil was oil, so to speak, and you could put whatever you wanted in a European car.