unsafe product

The beginning was good. The delivery time was very short and also the ordered product was apparently the packet. Unfortunately, my car repair shop has rejected the use of the product. The authenticity of the product has been questioned. The use could only be done under exclusion of any liability on the part of the workshop and VW at possibly occurring damage to the engine.
An inquiry to the obtained product at Castrol Hamburg have not dispelled these doubts. The nice colleague of Castrol Hamburg also knew of well-made counterfeits. Your recommendation was abzuverlangen the COA of the dealer, which is available every official distributor of Castrol oil.
My attempt to phone to contact autoteile.de failed always. There were permanent all colleagues talking to customers, as announced to the answering machine. In e-mails containing the request from the sending of the authenticity certificate, was not responding. The same behavior was also evident in contacts through Amazon.
If it had been an original product of Castrol, the COA would certainly have been no problem.
I have not used the product since the damage and the subsequent anger, even if you had taken the supplier's liability, would not have been proportionate. (Oil analysis 200, - unforeseeable workshop costs, attorney fees, no end of trouble ...).
I'm not going to acquire this experience through such products, which engage in the "life" of a car, again in this way. Thanks to Amazon and the "az guarantee" of, it was the end at least no financial loss, for which I would like to thank Amazon. The customer unfriendly dealer I would take the part of the Amazon offering.