I always witnessed a decrease in performance in the oil when it starts to get locally blended. Im not going into technical but just sharing my experience.
I used to used to use Shell Helix Ultra (originally Made and blended in Singapore) but then it started coming in different packaging and as soon as i start using it i did notice a drop in performance if only a minor one. I called up my friend who was working in Shell at the time and he told me that Shell have recently started local blend.
Same happened with Mobil1. First Made in Germany (contrary to people seeing Made in USA) then made in singapore and finally locally blended.
So ive switched to LM Synthoil since i believe its 'untouched' from Germany. Ive also had good feed back from Castrol Magnatec.
I am not saying that that companies blending locally intentionally hamper the performance but might be something to do with the blending procedure, machines etc.