I all depends on the kind of usage ...how many miles you drive and which conditions you drive in and what weather you drive in...butt a general idea of changing oil is around 3000 KM
if you use a standard grade oil and please don´t use heavy or thick oil because then you are not only destroying you engine butt infact you are using more fuel for less mileage.
On the other hand if you do not drive all those miles then chande the oil every three months ...so KM 3000 or three months which ever comes first.