Loud tapping noise from engine

[nene]

Update:
The noise has not returned. I have not driven the car hard at all but took it around town for about 30 minute drive. Checked for any engine codes after the drive and nothing.
Left the car overnight and did not restart the car until almost 24 hours later, and the noise still has not returned. Checked for engine codes and all is still clear.

Checked all my past dealer work orders where oil change was made and it seems one of the 2 below were always used:
G052167A2 (discontinued by Audi superseded by M2)= Castrol TXT 505.1 5W-40
G052167M2 = Castrol Edge Turbo Diesel 5W-40

Checked the last invoice, which included my 70K mile service, and part number for oil was:
G052167S0
A quick search on the net and it seems it is 'Castrol Syntec 5w-40 bulk oil'. Oil weight seems correct, and I trust the tech that did the work.
Nevertheless, I have sent an e-mail to BND sales and requested their formula for the RS6. Waiting for a reply, and will order it as soon as I possible.

[mrdave]

Checked the last invoice, which included my 70K mile service, and part number for oil was:
G052167S0
A quick search on the net and it seems it is 'Castrol Syntec 5w-40 bulk oil'.

And this is exactly why I always do my own maintenance. As DHall1 said, I would not run that oil in my car. The weight may be the same as the proper spec but the additives are likely way off. I've also been using BND and have been very happy with the quality.

[DHall1]

Its funny really. My wife wanders out in my shop/2nd house every now and then and asks why we have so much BND oil on the shelf. " is that new oil?" Yep "How many cars will that stuff fill?" Let me see, we have 4 Audi's an AMG and one diesel pusher. About 66 quarts should do it, any other questions? :-)

That 5/40 Syntec crap is exactly why Audi sent out the service bulletin back in the day.

Use 505.01 oil in the RS6 or you will void the engine warranty.

Its really that simple. The loads placed on RS6 engine oil are critical and need the proper spec.

I had a hunch that dealer used the wrong oil in Nene's car.

And this is exactly why I always do my own maintenance. As DHall1 said, I would not run that oil in my car. The weight may be the same as the proper spec but the additives are likely way off. I've also been using BND and have been very happy with the quality.