I searched the forum alot about oil and I came up with this thread.

https://www.audiforums.com/m_16044/tm.htm

It says that Castrol Syntec 5w-40 is ok to use. I just got a oil change recently, but they only had Castrol in 5w-30, I won't like get oil sludge or anything just because I didn't use 40 right? I know oil questions get asked all the time, sorry.

 

basically as long as it is synthetic oil you are golden

 

Ok cool, I called my local Audi dealer and they had told me that an oil change would cost me $65, is that how much it usually costs? And does that just include the oil change or do they check other things too?

 

$65 sounds about right for the dealer to change your oil. It says in my owners manual that 5w30 is ok to use if 5w40 is not available.