Actually, I wouldnt recommend using GL-5 at all in our trannies. There's a reason that The FSM says use GL-4 in the tranny and GL-5 in the diff. GL-5 has been known to destroy brass syncros and I wouldnt even dare think to run that thing in my car.
Now on topic for MT-90. I love that stuff. Thats makes my tranny shift so smooth. I personnally run 2.5 bottles (quarts) of MT-90 myself. Love that stuff
I've used redline Heavy Shockproof before and man that takes a long time to get warm. My tranny would shift rough for about 5-10 mins but after that, it was the smoothest oil I have ever used in my tranny. Personally thats too extreme for me since by that time, I've already made it to school and the tranny was shifting roughly all during that time. THen again I used 2.5 of shockproof instead of mixing it as you plan to do it.
Also I get my stuff from
http://myoilshop.com and use dealer discount code 675421 and get an additional 10% off from the already cheap prices.
+1 for MT-90 though
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