Lets just assume the question is why there is an american motor oil and a european motor oil with the same 'labeling'.
Europeans have access to some very fast roads that they may use legally and drive near the speed limtis of their cars. *That this can only realistically be done at 3:00 AM in the morning is immaterial.}
Americans only have access to roads where 85MPH is legal *horay for rual interstates in west Texas}.
Second, Euopeans drive at these higher speeds in cars with rather small engines (compared to typical american engines). So instead of doing a land speed record attempt in a 6-7 litre motor, the Europenas do it in a 2-3 litre motor. This puts the internal stress levels significantly higher in these smaller motors, and this happens at higher RPMs than many american cars ever see. All of this leads to a need for very good HTHS numbers.
Effectively, these xW-40 based Euopean motor oils are a little thicker in both the startup and operating viscosities and usefully thicker in the HTHS viscosity numbers. The fuel economy numbers may be down somewhat.
