I agree with Sprintman that "SLX appears out of the ordinary for NA". I would add "for the moment". It may happen that that this euphoria will disappear soon like the first snow. In Europe it was never considered the best, but always after Mobil 1 0W-40. To meet OEMs requirements, as well as to compete with Mobil 1 in aftermarket sector Castrol had to make 0W-40 version of SLX.
0W-30 is very good oil indeed, but volume of its sales never met Castrol expectations and probably fully justified investment, where, I suppose, sales under Veedol brand too. Apparently the main obstacle was its SAE 30 viscosity since in the second half of ninetieth European end-users were not yet ready for this 1) phsychologically (prejudice), 2) cause of majority European OEMs recommendations. Even now BMW uses for services exclusively its 0W-40 version (BMW Quality Longlife-01 0W-40) despite Formula SLX 0w30 is also approved by BMW. 0w30 is used by BMW services, but in 01FE version. Theoretically Formula SLX would be great for the majority of NA and Japaneese cars, but I shall not use it in Prelude 2.2 VTEC before I get a clear picture why Honda does specify neither 0W-30, nor 0W-40 for this type of engine.
To tell the truth, I expected from GC considerably better performance, but what I could see in used oil analysis presented on this site, there is nothing exceptional: 1) results are in the limits of analysis error, 2) engine work and oil stress for indicated periods are not equal even if we believe or feel they are. Therefore, these used oil analysis cannot serve a base for some comparisons, but just show a trend.
As for virgin oil quality, think it would be interesting for all of us to know whether and how Formula SLX sold in Germany differs from country to country. So, let's see how can we make it.
In addition, has somebody already tried Castrol Formula GM 0w30 ?