Hi, It is time to change my transfer case oil on my Yukon Denali 2007 and I have a critical question which I hope you can help me out before I do something wrong and damage my T-case. The 2007 owners manual says I shoul use the following (Manual transmission Fluid GM Part No. 88861800.) However, my father's 2009 Yukon Denali manual as well as my friend's 2012 same car say they should use DEXRON-VI Automic Transmission Fluid! As far as I know there has been no changes in Yukon Denali from 07 to 2012. Therefore, this made me feel a little bit skeptical about my 2007 manual. So my question is: should I use DEXRON- VI or GM Part No. U.S. 88861800 for my T-Case? Please help me out!