i have a 94 civic 5 speed. I checked Alldata today and it says the transaxle uses 10/30 or 10/40 motor oil in it. It also said SG. Is this right? And does anyone know what SG is?

How often should I change my trans oil? i'm guessing every 30-50K.

some places just put in 10w-30 oil in trannies just like in their motors. I always use the true honda transmission fluid tho. 10w-30 works tho if you REALLY need to use it.

should be replaced every 30K

Honda manual transmission fluid is only Valvoline 10w-30 motor oil - just a different bottle & sticker.

SG is a rating
http://www.edmunds.com/ownership/driving/articles/44791/article.html