[Houston1960]

Thanks a lot for your answer, I was concerned about it because I have a 2011 Acadia and I purchased several month ago, a 2014 GMC Terrain and I went to buy 5W-20 full synthetic oil, assuming that it could be as same as the Acadia, but when I was going to take the oil cap, I saw that it says 5W-30, I went ahead and used the 5W-20 on the Terrain which is 4 cylinders, I thought that smaller engine as 4 cyls should use less viscosity or the same as the Acadia which is 6 cylinders, but seems that I was wrong, that's why my question, because the bigger the engine the more viscosity should use, but now I know that is not the case, thanks again.

 

[Houston1960]

There is much discussion over on the Equinox/Terrain forum about oil viscosity. The 2.4L oil spec was higher due to the tendency of oil consumption due to blow by and common 2.4L engine issues. GM even had a TSB regarding new piston, rings etc.
The newer +2017 t0 current Acadia 3.6L LGX engine has tighter clearances and higher oil pressure than the 2.4L 4 cylinder and still takes a Dexos 2 certified 5W-30 according to my owner's manual and what the dealers put in for an oil change.
However, there has been a change in oil filter from the previous AC PF63e to the pro grade AC UPG63 due to the higher oil pressure and need of beefier construction.

Wow that really helps and explains why, now I understand thanks very much again for you quick and helpful answer, you have a great day.