Originally Posted by Surly73
I prefer to select a fluid which is designed from the get-go as a manual transmission fluid, not an ATF which happens to work OK. This is why I usually stick with Redline MTL or Amsoil MTF - designed for MTs from the start. ATF does have friction modifiers too, but the design parameters don't necessarily match MTs.
I appreciate your reasoning and will be deciding on a fluid next year for my E91 and 128i. MTL worked very well on my E46 5 speed, but why do you think Red Line recommends D6 for the E90, rather than MTL?