I have a 1983 300D, and I'll be changing its transmission fluid pretty soon. What with Dexron II not being an option anymore, what specification would you guys recommend as having the best backwards compatibility and being most appropriate for a thirty-year-old transmission? I've been told Mobil 1, but other people said no, they changed their formula, you shouldn't use them now. The guy at Autozone said the new Dexron VI is completely compatible, so just use it, but it was my understanding it has different viscosity characteristics. Am I wrong?

I suspect asking about brands could start a war, so I'm not even gonna go there.

Thanks for any help you can give me!