I think that I have chimed in on just about every thread asking about mixing oil brands/grades/weights.
I've been mixing for over 35 years and never a problem. I usually keep my vehicles into their teens with several hundred thousand miles on them. Back then it was due to lack of money or I was just looking for cheap oil for a beater.
My most famous mixes were when I used 5 different brands of oil, each brand being a different grade/weight... Engine ran fine!
Today, I have so many different "name" brands/weights/grades of oil in my stash,(all oils are held in high regard here at BITOG) that I have purchaced on sale/rebate/closeout. The oils that I mix today consist of some Syn with dino and/or some 5W20 w/5W30 especially in the winter. In the summer, I may use some 10W30 w/5W30...It all depends on what I have in my stash at that time.
My stash consist of(DINO-GTX, PYB, Valv, Hav, Chev, Peak) & (SYN- PP, M-1, QS/TP, ValvDB). All good stuff today!