When i top mine up, I just use what BIKE oil I've got in the shed. Usually, 10w40 semi.
I dont restrict it to bike oil, that new container of diesel engine oil that my son foolishly left in my garage, is going in next oil change

mind you, I use car engine oil in all my bikes, despite others saying I must not, apparently it fecks the clutch, I remember a time when car engine oil used to be from a huge drum in the main honda dealers, my clutches seem ok so far