[Gustav]

With a sealed diff you use different weights of silcone oil but i don't think this is a sealed diff (i may be wrong-happens quite frequently-lol).If it's not sealed then don't use silcone,it'll just ooze out all over the place.Instead you can either just use a regular grease to run the diff quite loose or you can use a thick tacky grease like tamiya anti-wear grease for more limited-slip effect.