it will be fine, if its a mineral oil it will degreade the properties of the oil currently in the engine, if the oil in the engine is of a superior quality.... what also troubles me is why he recently topped it up? where is the oil going for it to be required to be topped up?
from factory they use ELF 5W40 and about 5lt of it.
I think Renault say 1 litre per 10,000 miles is normal, if I'm wrong I'm sure someone will correct me.