170, sometimes the ex Hull Trains fleet with the buffets. 158s are much rarer now and it tends to be a single 170 that goes up there. AIUI, 1tp2h north of Perth is sufficient with a single turbo. (Connections at Stirling and Perth are well advertised). The 158s up there tend stick to Aberdeen, Wick and Kyle services now, but I'm sure they'll make an apperence from time to time.