General: how not to treat an autobox - Roger Jones
With permission, I quote from a contributor to the MB Club forum:

"A friend who worked for Borg Warner in the 1980s told me this afternoon that the majority of factory rebuilds were due to people topping up with gear oil instead of transmission fluid. The resulting black goo tended to cause the valve block to become obstructed, leading to rough shifts etc."

I wonder how much of this is still going on.
General: how not to treat an autobox - Aprilia
Find that very hard to believe, to be honest. I think that's a bit of an urban myth.
General: how not to treat an autobox - Roger Jones
Well, don't shoot the messenger. I've no reason to disbelieve the intermediate source and I do wonder why the original source should have made it up.