mixing transmission fluid types

A long-running question. I decided to use ATF+4 in my old Mopars since I learned it is fully synthetic. The Autozone brand seems as good as the others when I read the back. Currently, I have Type F in my Newport's 727. I read that "F" means "friction", i.e. more friction modifiers than Dexron. It is also used in many Fords, so people say that explains the F. Since then I read that ATF+4 has even more friction modifiers than Type F, so it seems better overall. I recall Mopar info suggesting Dexron best for older trannys, but that might have been before ATF. More friction is good if you want your clutch plates to last (fast, firm shifts).

Where it really mattered was the first Mopar electronically controlled trannys (A604, etc) in most V-6 minivans. ATF was rare then so some Mopar marketing genius had the owner's manual state that one could use Dexron when ATF wasn't available. Tranny shops took that to mean they could use cheaper Dexron at will. Many transmissions failed from that little comment. They would "shudder" and burn up the clutch plates with the slippery Dexron (plus controller instability?). A big black mark for Chrysler.