It's getting time to change out my 5HP30 ATF fluid and I noticed that our old standby, Pennzoil Multi ATF has changed formulation back to mineral. I'm kinda hesitant to go non synthetic.

What are you using these days? Castrol and Mobil One have LA2634 complaint synthetics, but I've never used them. Amsoil also has similar claims.

This will be the first change for my Kirt rebuilt 5HP30, and don't wanna muck it up.

Thanks

Ramon