To add and keep on with where chester was going.
For the 3.5l engine, you want to stick with synthetic 5w30, or if you live in cold country like me, 0w30.
The oil filter should be a generic number with the 4 last digits being 1040 for NAPA or WIX and that type. Maybe even walmart has same number. I know my local canadian tire uses 1040filters.
Interval should be no more than 8000km. I wouldn't go by the GM oil life system. I would rely on a good old school sticker some where.
Do you really need the dexos designation? I say no. Any full synthetic will more than surpass the dexos norms. But some may disagree with me, and I invite NO debate on this. It is just an educated opinion. The dexos debate is like kicking a dead dog.
Oil filters are another useless debate, kind of like which battery is better. There are only so many companies in the world that mass produce stuff. I do like the FRAM filters just cuz they are convenient with the asphalt like coating they put on the end, it does grip better even if your hands or gloves are covered in oil. But does that justify the 4$ more?
Apart from that, I guess we could go in the micro filtration side of things, but in todays standards, any generic stuff will more than surpass OEM when it comes to lubrication. The after market for this is very large and alot of ppl want a piece of the cake. Marketing is key. But when you change your oil at regular intervals, with any kind of oil filtration device, I have rarely seen engine failure.
Give the same well maintained car to your daughter or son you just sent off to college. Give him or her a sweet ride, but don't remind these young ppl with an app on their smart phone, what do you think happens?