Sorry.  Sarcasm was intended.

I am a firm believer in Cenex oil and pretty much run it exclusively, but I have not turned down a free oil change from the local Chevy dealer with GM oil since GM engineers speced the oil.  However, I have turned down oil free oil change (door prize coupon) from local shop that uses cheapest flavor of the day. with both oil and filters.  The OP refusing to use free oil change with OEM speced oil because he feels his Mobile 1 is far superior and GM oil is like water warranted a sarcastic comment.