mmmm... I don't see how You can drain it all easy but You can drain some/most of it and refill with lucas ps additive that renews the old fluid or run the ps pump with the return hose disconnected. Also and this is just Me, You can run it until the pump or gear box gives up a seal (if You haven't changed anything yet) You know once something is working well is better not touching it (that is My experience again), is not like a transmission or engine oil.