Yes, my friends,
Oil is Oil. As long as you do not mix up vegetable and mineral, and that's pretty hard to
do in 2018, since Vegetable is so hard to obtain, then just about anything will mix with just about anything else without any ill effects.
And why are you topping it up anyway?
Last year, I set off for Morocco and a 2 week trip.
Did not check the oil before I left, and did not check it throughout the trip.
I do not regularly check the oil level in my car, so why should I do it in my bike?
The car is much more likely to suffer from low level damage than any motorcycle, given that the contents of the sump are subject so surge on cornering, which is not the case in motorcycles. (unless you wheelie!)
Stop obsessing, relax a little.
Myke