This boy totally agrees, if the manufacturer states a certain oil I'd adhere to that. We have the same utter confusion here too, don't know about Germany. I remember having cars that weren't fussed, a 20w 50 oil seemed to work in all cars from the 60's to 70's then it all went nuts,this spec, that spec one grade of oil wasn't suitable for all cars, you had to study numbers, letters and Lord knows what else.