The oscillations will violate conservation of lepton family numbers,,. This is because in neutrino oscillations, a neutrino oscillates between lepton families. For example, a neutrino could oscillate between an electron neutrinothat has,,and a muon neutrinothat has,,which obviously violates conservation of lepton family numbers.
On the other hand, because a lepton is never formed or annihilated during an oscillation - a single neutrino is merely changing lepton families - there will be no violation of the total number of leptons conservation law.