Then there seem to be different instructions for the European sold engines, and the US sold engines???

@ Alta..,

Synthetics indeed have quality differences, depending on base stock just as much as the quality dino oils. One of the quality benchmarks is the ratio in which the oil can be mixed, and still do a decent job. This has to do with the property that lets the oil cling to metal surfaces. Let it cling too much, and it will be very hard to replenish the oild oil with new one. With dino oil, this process took about one hour engine running time, during which the engine ran worse when switching oils. With the best synthetics, this process may take up about 5 running hours.
Another quality benchmark is the range of allowed mixes. I would prefer an oil that can be mixed anywhere between 4 and 1 %, and then mix it at my 2.5% ratio that I like best for a nice and slippery wet engine.