fully synthetic gear oil?

[Jin]

hi all
just a quickie
after spying some dampness around the gearbox area (that may or may not be a slight leak but un diagnosed as yet) i thought i would see about changing the oil and fully topping it up since i don’t know how old it is nor how much is in there, so first port of call was ebay since nowadays it seems cheaper with postage from the like of euro car parts than going to hellfrauds even with trade card.

first lot i go to was a good make fully sympathetic gear oil in the right viscosity and it got me thinking...

should i? shouldn’t i?

from what I’ve read on the net some people swear by it, some people swear at it

what do you guys think?

cheers