[V8] Synthetic Oil

[Brad Hartman]

My newly-acquired 2000 A6 2.7T came with a fresh change of Pentosin 
Synthetic oil.  I thought it would be smart to buy a quart or two of 
replacement oil just in case I have a need to top it off before the next oil 
change.

O'Reilly Auto Parts has Standard Mobile 1 on sale for $5.99 a quart.  Is it 
OK to add Mobile 1 to a car currently filled with Pentosin Synthetic?

Also, Mobile 1 is offered in different varients (Standard,  Extended 
Performance, Advanced Fuel Economy, etc.)  Any suggestions?

Thanks,

Brad