I had 10/30 in the tranny for a month before it started to leak and make noise and grind gears after it got rebuilt. Recommend Redline MT90. Quiet and it does the job in replacement of the Hondas mtl.

 

i've been running mobil 1 10w30 motor oil in my 2000 si for over 2 years. exedy clutch, 75 shot of n20 and about 75 passes down the 1/4 and she still goes into gear fine and grabs nicely. some may disagree but that's what i do.

 

I also run mobil 10w30 non sythetic and it seems to work just fine for me :dunno:

 

I never seen a manual that said 10/40 was ok in a honda/acura.

i have seen 10/30 before Honda brought out the mtf. I have 10/30 in my 00si for ease of replacing.(try putting the mtf in out of the bottle, it sucks)

I just shoot the oil in with our lube gun.
The trans will probably just need bearings though, no big deal.

 

I use Mobil 10w30 in my civic tranny