Can I use Amsoil or Royal Purple synthetic?

Also why no dex 6 for t case but ok for transmission?

 

Redline is the best as it is the only Class A syn oil period (I believe class V), then following Redline is Mobil1 and Royal Purple and Amsoil which are Class B. I use Redline in all holes except the engine as Mobil1 is more available at Walmart and engine oil has to be changed more frequently.

You will notice that the Transfer case and diffs will burn up oil before they intended change intervals. This is even more of a reason to use Redline here. Also Redline is the only one that makes true Dex-VI tranny fluid where Amsoil says to use their multi-use tranny fluid that does not fully meet the Dex-VI specification. Amsoil is nothing more than marketing BS is they expect us to believe getting close to a spec is acceptable. It's certainly not acceptable to the vehicle manufacturers!

GM specs Dex-VI for all new trannys even older ones that previously stated Dex-III as the D6 is better fluid with larger viscosity range. The transfer case needs the thicker viscosity of Dex-III as it's just a "gear box". My suggestion is to use the Redline D6 tranny fluid and their High Temp ATF Dex-III for the Transfer Case. Their high temp ATF D3 fluid will hold up best in the TC.

Royal Purple would be my 2nd choice but since they dont make Dex-6 tranny fluid or a high temp D3 for the TC, I suggest redline so you can stick with one company for all your needs.

By upgrading to a higher quality fluid such as Redline, you will notice that your H2 drives slightly smoother if you notice changes easily such as I do. I hope you find this information useful

 

Hummer h2 front axle and rear axle 75w90 oil change cost $150