I am concern too.
I suppose the letter came out to make sure that in the future that I don't change to regular oil. And I also got an ammended lub requirement booklet.
I also heard that people got recent oil change and it was regular oil on their ml because it said so on their worksheet.
But, I sure like to be able to tell.
I guess I just have to trust them.
Like I said before thank god they are working on my car and not my health.
Silver Honda Accord, 2006
Silver G500, 2003
Silver SLK-320, 2002
Black ML-320, 2000
Bule Porsche 993 Targa , 1997
Silver Merkur XR4Ti, 1987