do you need a sealed diff to use heavy diff oil?

[jebster]

i have an old buggy (inferno 10) and want to use it for foff. i don't want to lock the diffs, just stiffen them up. any suggestions on what i can use? it isn't a sealed diff so i'm not sure standard diff oil (say 100k) would stay inside and not leak out. i don't know how thick diff oil is since i don't have any around. if that won't work how about some automotive grease? recommendations?

inputs are appreciated.

[Jay-Em]

Diff-oil will be squeezed-out in no-time short.
I have good experiences with Tamiya's grey/silver AW grease. it's sticky as heck.

Asso Black Grease also works