Sometimes you also have oil leaks from the seal of the box distribution. Then checks that there are no streams of oil from the bottom of the box and along the lid of the cup. At this point you have to tighten the bolts evenly distribution of the box. You must also check that there are streams of oil spilling out from behind the pulley, since it would mean a loss of seal. If however, you realize that this happens, you have to go to a mechanic to show thee replace.
Sometimes losses can come from the side cover gaskets. This happens to some cars fitted with one or more plates of protection for the room of the tappets on one side of the engine, usually under the supply manifold or exhaust. If you realize then that the lower edge of one of the plates is a loss. But if the plate is located under the exhaust manifold, it is good to let the engine cool, though still warm, before proceeding.