I will be helping a friend change the fluid in his 2011 GMC Yukon with a 6.2 liter engine and AWD. The owners manual specs Synthetic 75w90 but does not mention limited slip additive and actually does not differentiate AWD from conventional 4WD. I plan on using a synthetic 75w90 with LSA built in. Does anyone know the story if built in LSA is sufficient or if typically it needs a separate limited slip additive? (If at all). Thanks.