I just changed my Tranny oil and used MTL. At first, I was not happy. Shifting was very notchy and a bit stiff. Since my NSX only had 17.5k miles on it when it became mine, I'm sure the fluid was factory original. I was going to put some new Honda lub in when I noticed the next day the shifting became very smooth and fluid. Don't know why but just from the oil sitting there in the tranny over night, the shifting was great. The only thing I can think of is the MTL needed time to "soak" into all the right parts of the tranny. If you try MTL or the heavier stuff, give it a couple of days before making your final judgement. Good luck.
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1994 Green-black roof/tan, 5 speed
Stock as a rock - #0030