There are many answers that you will get. Most of them, if not all are really unfounded.
Some will say yes you can, no problem, mix whatever
Some will say no do not mix at all
Some will say mixing just to make an oil change is ok, but dont make it a habit
Really up to you.
I am in the camp that in a pinch or just to get rid of oil, mixing the two should be fine, but i would not make a habit of it just because it might be thought to be of some advantage because there is not.