I recently did the first oil change on my 04 Golf TDI-PD, and had a friend pick up the required 505.01 oil from the dealer as I wasn't able to get there while they were open.
When I got my hands on the product, which the parts department had assured me was synthetic (and at $11 a litre, it sure ought to be!), I found the label described it merely as a "sythetic blend", which I understand to be weasel words for "contains a bit of synthetic oil". The product was Motul Specific 505.01 SAE 5W40 Technosynthese.
I then went to another dealer, who had recently dropped their price for the Castrol 505.01 product from $11 down to $8.40/Litre, and inquired about their product. The parts staff there assured me that they had been told it was 100% synthetic, and this was seconded by a technician, and later by parts staff at a third VW dealership.
However, this Castrol product, labbelled simply "Castrol 50501 5W-40 Special Motor Oil" carries only a description in German on the back , and this says only that it's a "special light oil designed for pump-injection diesel engines. The rest of the sticker is devoted to warnings about protecting yourself and the environment from the toxins in spent oil.
There word "synthetic", or its German equivalent, isn't to be found anywhere on this package.
I've been using nothing but fully synthetic engine oil in all of my vehicles for more than 20 years, and find it very maddening to now be forced to use a non-synthetic oil, and even have to pay through the nose for it.