VX Tranny oil Q
 

I was just wondering what oil people are running in their civic trannys for FE. The manual says 10w30 or 10w40, so i bought mobil 1 synthetic 10w 30, but I haven't put it in yet.

manual trans oil for VX
 

That's what I have used. It's goooooooood!

My first 92 VX had the same Mobil 1 10W30 in it for 10 years. I filled it after the first 500 miles when it was new and never had any trans issue i.e. the dreaded mainshaft or input shaft bearing noise.

My current VX also has Mobil 1 10W30 which I put in at 126000. Now it has 156000.

I run GM syncromesh on all my honda transmissions, no trouble yet after 3+ years.

Don't use normal motor oil. Those manuals were written many years ago - oil formulations have changed since then. Synthetics doubly so. Modern motor oils have additional friction inhibitors that cause the syncros in Honda transmissions to slip too much. Too much slip means additional wear and potentially grinding gears.
Honda sells their own MTF (manual transmission fluid)... It's just motor oil made to the proper spec for Honda manual transmissions. Unfortunately, it costs something like $5 a quart, but it's the best thing you can use.

the best thing you can do is make sure that it is changed, putting any new fluid in there that meets the required specs is going to get the sludge and grit out, and give it new lube to keep it going longer, the manual states that if motoroil is used to change it every two years, I can't imagine that there are more then 3 cars out there over 10 years old that have had that done.
I have 5w 30 Amsoil full synthetic MTF that is listed as being compatible with honda's and haven't had any issues.

Hmmm. I think I will go on the safe side and try amsoil or something similar that is designed for manual trannys. I had that similar issue with friction modifiers when i was researching the best oil to put in my friend's nighthawk 450, apparently the friction modifiers can make the clutch slip.

When you use friction modifyers in a motorcycle your main option is to flush the crank case really well, replace the clutch friction plates, scoure the presure plates clean, put it all back together, and add one of the many oils that is labled as being wet clutch compatible.

the only issue I've had with the amsoil MTF was when I put it in a tranny that had an already worn out main bearing (220,000 miles on it) and wasn't thick enough to cushen the slop in that bearing, but if your tranny is smooth and quite, then it will only improve it.

The consensus on the Honda forums seems to be Honda MTF as the preferred choice. That said, I just replaced mine with Royal Purple 10w-30.

Is there any feeling that in hotter climates, i.e. where it gets up to 100 and never goes below freezing, that MT-90 would be better?

Well, the transmission casing is a block of aluminum (a good heat conductor), directly bolted to the engine - another block of aluminum which heats itself up to a consistant 180?F during operation. In comparison, I don't think ambient air temperature is a heat source you need to worry about. I'm not even sure you would see a significant internal temperature difference if you were to compare a transmission operating in freezing conditions to one operating in 100?F temps.
Unlike the engine, the lubrication demands of a manual transmission are pretty mild - it's pretty much just a bunch of gears and open ball bearings. It doesn't even have an oil pump... It just relies on oil being picked up and carried around by the gears. Realisticly, I think a thicker lubricant (MT-90 is thicker than 30w oil, right?) would only result in additional drag and reduced fuel economy.