Some scattered thoughts for what they're worth...
-- European companies can't call a group III base oil 'synthetic' the same way manufacturers can in the U.S. This suggests to me that if a European product says it's synthetic it should contain at least a group IV (PAO) base. (my assumption...)
-- Absolutely DO disregard API specs in your search. In the ladder of oil performance (overall quality?) and certification severity, from low to high, think API, ACEA, Specific manufacturer spec.
-- Your goals and a manufacturer's goals might not be in harmony. You might select a better lubricant because you're looking for a 300,000 mile engine -- while a manufacturer might be looking for something 'good enough' to get past the warranty period, or improve their corporate fuel economy score, or stop ring sticking...
-- An engine oil is a complex brew consisting of 75-80% base oil and 20-25% additives. The cam wear issue that we think 505.01 is aimed at suggests we need more than just the normal protection of a hydraulic film (or someone thinks we do) - it suggests we're getting into the physical contact area that anti wear and extreme pressure additives do their thing. The usual additives, ZDDP and calcium, show up in oil analysis. There are other compounds that don't show up. Maybe the 505.01 oils (which appear to run the range from pure petroleum thru blends to group III to group IV) are something 'average' with a bit of esoteric EP/AW additive. Dunno yet.
-- Warranty...there's no such thing as 'a warranty'. Most manufacturer's warranties are for defects in materials or workmanship. Service reps or managers that really don't understand, and possibly those that do understand the warranty issue but 'spin' the words they use, often cause intentional fear in the customer so he/she 'plays it safe' and brings the car back to the dealer for parts and service (where dealers make most of their money) because it's easier than really figuring things out... If one chooses to use Quaker State SL (gas) oil in their PD, and the camshaft completely rounds out, Federal Law says the dealer must prove it was the lubricant that caused the problem. While that's going on, one service bay is occupied, and the vehicle owner will probably get a rental car on the dealer's dime. Instead, the dealer will point it back at the vehicle owner knowing that the owner will fold most of the time. Hmmm...kinda like health insurance. A wealthy person can pay cash when they get sick so doesn't pay health insurance - and isn't bound by the rules of the HMO. VWoA says they'll 'cure' the engine if it breaks as long as we use the approved products. You're free to use whatever product you wish as long as you also 'self insure'...
Nortones -- Group III base oils are definately of differing qualities - from batch to batch and from source crude to source crude. Group IV and V bases, tho, are consistant. To be a PAO it's got to be constructed of specific raw materials with a specific process. Think group III as water pulled from many wells across the world and run thru filters and bottled. Think group IV and V as water constructed in a lab environment by reacting hydrogen and oxygen. One is inconsistent and may contain all manner of impurities, and one is pure.
04Wagon: VW defines the requirements of the 505.01 spec, but isn't in the product certification industry. It's up to the manufacturer to test (or have their product tested) to ensure it's up to the requirements. Motul or Castrol certify their products, not VW. I wouldn't put any value one way or another on a response from VW on oil certification, unless you're asking about the nature of the spec - that's the only thing under VW's control - and the only thing their insurance company is responsible for covering...