There's really no reason for doing it. Using aftermarket brand oil and filters doesn't void your warranty, besides, I would bet a steak dinner that most, if not all of the car company branded oils and filters are made by aftermarket companies anyway...
I understand that I don't HAVE to use the manufacturers filters when under warranty. I just think it is one less thing to have to fight if anything should ever happen with one. GM had a bulletin out about two years ago that if an engine noise was heard, to first check the oil filter. It was found that some after market filters had failed and GM voided remaining power train warranty for the owners.
There was at least one owner who posted about a destroyed engine on the Enclave forum which was caused by a failed after market filter. GM did not repair the engine under warranty.
Other than having owned only one "foreign" car (Acura), we have always had Fords and GM's. Ford filters are more than sufficient, and so far I have still been able to use the "old" oil filters for the GM's, not the E-Core ones. Not expensive at all either when purchased other than at a dealership.
