Something I posted awhile back on the Toolbox Essentials sticky thread in this forum:
Kwicko said:
Transmission oil. Two ways to go here - Honda is NOW recommending their Manual Transmission Fluid (MTF) for *all* their manual transmissions and gearboxes. In the old days (when our cars were made), they recommended plain old SAE 5W-30 motor oil. I've used both with great results. Nowadays, I usually opt for the MTF, since Honda *recommends* it, but 5W-30 is just fine, too.
Just to expand on this section:
From what I've read, the reason Honda changed their official stance from 5W-30 to Honda MTF is because the makeup of motor oils has changed substantially from the late 80's/early 90's to present. Oils today have a lot of additives, detergents, etc. that are great for use as a motor oil, but not so great when you pour it in your transmission. Apparently Honda MTF is basically oil like it used to be, without the bells and whistles. If you must use 5W-30 in a pinch, it might be best to use some ultra-cheap store-brand oil that probably has less additives than more expensive, name-brand stuff.
Some people swear by GM's Synchromesh, too -- especially if you have a grind going into gear (it helps with worn synchros, hence the name). They sell a fluid premixed with the Synchromesh (which is a friction modifier), but the way to go is to use your usual Honda MTF and get the small bottle of separate Synchromesh (JUST the friction modifier, comes in like a 2-ounce bottle) to add to it. I've heard ithe premixed stuff is like 6 bucks at GMPartsDirect.com compared to like $15 at the dealer -- the modifier alone is probably similar. If you can't make it to a GM dealer (or refuse to set foot in one, haha) I believe Pennzoil and similar companies make a synchromesh.
Redline also makes what I've heard is a very good MTF...people who have used it and the GM stuff generally say the Redline is much better, and it's reasonably priced as well...others say that, in theory, it doesn't get along with input shaft bearings or something...I dunno.
No matter what you choose, remember to remove the fill plug before the drain plug on the tranny! It will drain better this way, but the main reason is that you don't want your tranny to be bone dry before you discover that you can't get the fill plug out to put the new fluid in -- especially if it's your only car.
Hope this sheds some light on what can be a somewhat confusing topic.