25k probably at upper limit of service on toothies... I've seen ones with 12k on them and the bearings are shagged (nick siggy) all depends how its driven.
could be breathing heavy, could be the charger oil seal weeping. With oil seal - you get oil, not oil vapour, which tends to be oily watery crap - if you've seen in a catch tank - its a horrid emulsified mess.