Transmission Fluid - really that hard?

[JFP in PA]

Originally Posted by Dlirium

I've read just about every post on this forum and others about recommendations for Transmission Fluid. Here are the two take aways for my 2000 Boxster S:

1) Correct oil for this is a GL-4 75W90.
2) Using a GL-5 in this transmission is BAD and will wear the yellow bits.
3) But, everyone uses a GL-5 (Swepco, Redline, Mobile1, etc) because that seems to be all that is available.

This feels very incongruent. What, pray tell, am I missing?

Everything. Porsche uses a unique gear oil (it has no Gl rating) that is manufactured for them by an obscure branch of Royal Dutch Shell. When we questioned several manufacture's about their products for this application, the larger and apparently more honest ones (Mobil, Castrol, etc.) stated that it is an unusual product with unique specs, and that they had nothing comparable to offer because of the small market. The smaller "blenders" all claimed to have the perfect match for it; only problem was that their "matches" caused noise, hard shifting and other problems, which promptly went away when their products were drained out and replaced with Porsche's OEM fluid, which is also a full synthetic.

It's your car and you money, we only use the OEM product.