I would have shifted to any good 10w-40 fully synthetic oil with established wear protection and API certified, if I were you. And don't forget to install an OEM (genuine) Honda Engine Oil Filter.
The R18 is a reliable long life engine and not too sensitive to viscosity changes at 160K on the odo.
By the way, if not done before, I'd suggest replacing the transmission/ gear oil (whatever the system is) along with the oil change. Just saying.