as viscosity increases rigidity thru the drive train rises, since cats are fix center units anything higher than 10k can produce drive failure before fluid stiff diff. ...like 30k is basically fluid locker...so too much is break prone, and steering falls off as things stiff up.
10k or less . higher in front lower in back , like 10k frt/5k rear and if your terrain is firmer the 7k/3k like grass. if loss stuff is present then 10k/5k may work better. wear is not an issue and for bash maybe change couple hundred hours but breakage will give opportunities as well . hope it helps
some terrains need it like sand /paddles