Been using it for 11 yrs since I switched to Ravenol. And it's written in the oil filler cap that Audi recommends Castrol, and all that stands. But I can't figure, why did they produce their own OEM oil, but recommended another brand oil. That's kind of gimic, it makes no sense, aldo maybe Castrol did make Audi OEM oil, but there's no evidence of this.
I don't know how deep did you go in oil making process, and never the less Castrol 5W-30 is a good oil, and you'll have no problem adleist in the short term, the differnece will show in long term usage.
Germany is the only country in the world that has strict regulations in oil branding and designation.
Castrol 5W-30, 507.00 is labeled as Full Synthetic in the UK, but in Germany is labeled as HC-Synthese not Vollsyntetisches like for instance Ravenol VMP 5W-30.
And HC-Synthese means that the oil is Hydro cracked from crude oil, and has a lot of impurities that are inevitable from crude oil plus added aditives.
Full synthetic oil like Ravenol VMP 5W-30, that is PAO, is made in a labaratory and every molecule is made to be let's say perfect.
The reason why most brand oils are made from crude oil is the price of manufacturing such oils that is cheaper.
I would like to be given a choice like we have in Ravenol, for etc. they have 5W-30 VMP(504.00-507.00) made from PAO and are full synthetic, and they have 5W-30 oil (504.00-507.) SMP that are made from 3rd group from crude oils and it's a bit cheaper.