I understand what your saying, same thing with my Evo 8 in 2003 had a Mobil 1 logo on the oil cap, but that doesn't mean Mobil 1 isn't bad oil? Or that it was the cheapest oil they could get? Maybe its the best oil they could find that everyone can get?
Same thing with VW. Who cares even if VW owned Castrol, Castrol Oil is good oil. When I had my valve cover leaking and crank sensor leaking they took a sample of my oil. What they did with it or whatever I dont know, but they did take a sample.
Every dealer works differently. What mine does is completely different than yours, but in my case? They look under my car for modifications, they scan the ECU for tunes, and pop open my air box even to check for the paper air filter. So if they are that picky??? I am using a 502 oil dont care what brand. The thing is, Amsoil, Redline and others do not carry the 502 approval. Sure companies can just pay for them, but they dont cost that much to get the approval so why not have it? People think its like MILLIONS to get an approval, more like Thousands. I think Amsoil and Redline both could afford it but dont.
The next closest dealer for me is 2 hrs away, and for warranty stuff like leaking water pumps, leaking oil seals and what not, I dont feel comfortable driving my car 2 hrs so I stick to my local dealer.
The bottom line is this. The oils people use that cost more like Amsoil, Redline, Motul, Royal Purple, and so on, cost at mininal DOUBLE what the Castrol 0w40 costs me and after a 100k miles I am sure my half price oil will keep the engine just as clean, wear just the same as those oils costing double if not triple the price.
Thats all I am saying....
Jeff