Is it bad for my snowmobile chaincase to leak a little oil??? Please Help!?

[skidoosleds91]

hey everyone-my snowmobile leaks oil out of the back after its been running, not when it sits. I just put the chaincase on and just tested it and everything seems fine except this leak. I guess its a bearing but theres no way im doin it all over again right now, maybe in the summer. Is it ok for now to just make sure theres oil in the case before every ride? And one more thing, I heard mineral chaincase oil is thicker than synthetic. Is this true? many thanx