I actually had an 08 Equinox for about a year. I ran QS HP( now Ultimate Durability )and it did well on it. QS, PP, VVL, Kendall, etc... Basically any name brand synthetic would be a good choice. Note that the 3.4L is known for startup valve train clatter( complain at a GM dealer and per GM warranty directions they time how long it takes to go away and it has to take longer than a minute before they will do anything )so IMO a synthetic is in order.
I would offer a filter warning however. I got a deal on some Napa ProSelect filters for $0.99 each( new - local Napa promotion )but couldn't use them as they caused the standard cold start noises to become HORRIBLE cold start noises. I went back to the OE AC Delco filters and things went back to normal. As I said above, the 3.4L is known for startup rattles/valve train clatter but it was REALLY bad when I ran those ProSelects.