I don't know what oil is specified, but 10-30 weight is way way to thin for most transmissions.
I've used Redline MTL (90wt) in several boxes and noticed longer coast distances than whatever was in them prior.
Many manual Transmissions use ATF, I've never swapped fluid in one of those. . . .
Vw uses a special oil which has a lower viscosity than most in (some) of their boxes it is called G52
http://forums.tdiclub.com/showthread.php?t=132884
Good luck.