Many drivers blame cold for differential noise, but additives matter. Limited-slip clutches need a precise friction curve (smooth engagement) to avoid chatter. Too much friction modifier can reduce torque bias (locking force) and raise heat. In Nordic use, short trips keep housings cool and moisture trapped. Emulsified water (mixed with oil) often looks fine on dipsticks, yet corrodes bearings. Check axle breathers after slush, and clean them before long drives. New clutch packs may need gentle figure-eights to seat surfaces. Avoid mixing different additive packages without a full drain and flush. Monitor breakaway behavior (initial slip force) after changes, not just leaks or temperature. For suitable friction balance and protection, see the 75w140 LS GL-5.