I just stick to genuine oil from TPS. Saves the squabbles lol
As with most branded stuff, peel away the label and it's all the same. It's down to the specifications of the oil (which is a string of numbers), I'll try and find the article I read a while back that describes what to look for. Although, as you say, buying the genuine VW guarantees the right spec for your engine when stock but maybe not when running any form of tuning beyond a 20% power increase.
I just wanted to help clear up the whole "Genuine VW oil" argument. I assume the oil you are referring to is the Quantum oil from both TPS and the dealership?
Just be aware that there is no such thing as "Genuine VW" oil. When you go to the dealership for a service, the oil they use wont necessarily be the quantum stuff - sometimes its Castrol, sometimes its Shell Helix - depending on who has the supplying contract at the time.
The Quantum brand itself is part of VW UK only (not VW the car maker). If you ask for Quantum oil in Germany, they wont have a clue what you are talking about as its only available in the UK.
Quantum branded goods range from engine oil to rubber gloves to light bulbs - and not just for VAG vehicles either. You might find a lot of quantum branded products in motor factors.
Quantum products are not the same as VW Genuine Parts - at TPS and some dealerships, you can buy both Genuine VW screen wash as well as Quantum branded screen wash for instance - they are not the same thing.
Im not saying Quantum oil isnt good enough for our cars - it is as it meet the VW 504 and 507 standards, but please dont think that just because you buy it from the dealership/TPS its any better or better suited for our cars (over other oil brands).
Quantum is just a brand that makes "automotive parts and consumables" for many different makes but just happens to be part of VW UK (not the Volkswagen Group)
Hope this clears things up.
Rich