Ohooo, I was not aware of that. So he is using a thicker oil already.
We'll, if the oil consumption is very minor over a long range of distance covered, thane it's fine. He may only need to top up.
But, if the oil consumption is high, with blue gray smoke from the exhaust then an engine overhaul may be required. Or at least top overhaul with piston ring replacement and engine head inspection and over haul.
Leakage of oil should also be checked out first.
PCV operation should also be checked.