Dude, you could use the auto parts stores own brand if you wanted to. The key here is changing your oil/filter at regular intervals. The oil recommendations are simply that....recommendations. You can also void the warranty if you drive the car normally. According to GM, driving the car over 50mph and over 3k rpm is considered aggressive driving. Ive never used the required oil in any of my cars (of course, I've never used synthetics either) and none have ever broke. 20w50 VR1 in the goat (9,700 miles), Casterol 10w40 in the '89 Century (122,000 miles and going strong), same in the '03 Crown Vic (106,000 miles).
But I digress. Everyone has a different opinion.
When in doubt, just use what the car came with. But I'd still change the oil no more than every 4k....no matter what the synthetics boast.
'06 Torrid Red M6