I tried the German Castrol and it made my car engine run real smooth. I like it, but I have some misgivings.
For one thing, there is no API Certification. Probably does not matter but if anything did go wrong they could maybe void your warranty.
For another thing, there is something wrong, in my opinion, that the German Castrol is so hard to find and that Castrol has not started to make it in the USA.
Stop and think about it: The German Castrol costs only about as much as Mobil 1. It seems to be able to compete with Mobil 1 as to quality and cost. So Castrol potentially has a Mobil 1 beater in the German Castrol. So WHY do they not replace the Castrol Syntec made in the USA with the German Castrol?