Tranny lube and EP additive Question

[glxpassat]

My tranny requires a 75w-90 GL4 lube, which is a 40w when hot. Redline makes MTL 70w-80 and MT-90 that are both GL4 rated. If I mix the two 1:1, I still get a 40w when hot, around 13 cst rather than the 15 cst of MT-90, so I think this would be safe to do and it would shift better when cold. The stock fluid is around 14 cst, so if anyone thinks it would not be safe, please let me know.

Redline also makes a 75w-90NS which is GL5+ rated and they state their EP additive is safe for yellow metals. Would there be a protective advantage to using the NS that has the extra EP additive with the MTL rather than mixing with the MT-90? Or would the extra EP offer no benefit and maybe hurt the shifting performance?

Thanks for any help!

 

[unDummy]

MT90 is a 75w90, so no mixing is necessary.
75w90NS is also a good choice. But, being a GL5, might not shift as smooth as MT90.

Does it really get all that cold in Alabama? I would just use the MT90 or 75w90NS as it is.

 

[ConfederateTyrant]

No need to mix, but as unDummy said, the GL-5 may not be the best feel for shifting. That is based on the posts on this forum that I have read. GL-4 appears to offer better shifting, so go with MT-90 or Amsoil MTG.

 

[glxpassat]

unDummy, I just wanted to thin the MT-90 a little and was wondering if the NS would be a better choice to thin since it has the extra EP additive.

I'm in North AL so it may not be an issue, I don't know. It gets cold here, but not severe. My VW tranny is pretty finicky on that 1-2 shift in the morning.

 

[glxpassat]

Thanks Tyrant!