When you have a vehicle that is new and on good synth oil there is no need to add anything.
For the most additives are great if you are trying to correct or mask an issue the easy way. Things like a sticky lifter in an old engine that has been setting things like Marvel Mystery oil will help but that would not mean I would put it into a new engine.
Use good oil, change it based on the DIC GM has given you and stick to the recomended weight.
GM is putting Mobil one in most of the new cars and I think they are using it in the Terrain too. Mobil is rated the new GM rating and is on the recomended list by GM. It is not as expensive as it used to be.
Keep in mind additives are like fix a flat You would not put it in a tire that is not leaking would you?
There are a lot of opinions out there. But the one that counts is GM's. They do not recomend any additives and if they had something that they felt would help them in their 5 year 100.000 mile warranty they would recomend it. Syn Oil is the main thing they recomend and 5W30 so stick with it.
There is a lot of snake oil out there some of it will not hurt but some will. I have seen many people kill an engine with things like Slick 50 etc.