Mike, as always, your sound advice is greatly appreciated. Here is what caused my post:
I am not in the position (yet) to do the oil change on the Audis myself, as I have no way (yet) to reset the service interval in the computer.
I did not go to the Audi service dealer this time, because there is a local shop around the corner and they advertised a synthetic oil change for $39.99.
When I checked in, they told me they could not honor the coupon, because the car, an Audi RS3, required "Euro" spec synth which would make the oil change $102.-
Now, of course I could do as you said and let things be, but I was just curious especially as I have been working on cars and motorcycles for 50+ years and I have a MBA in mechanical engineering and my thesis was in internal combustion engines.
In addition, my years of working for a supplier in the Automotive industry have made me notoriously suspicious of the things the "manufacturer recommends"