Answer:
yes, infact, 95% of synthetics are about a 50/50 of conventional oil, and synthetic anyways. mix and match all you want, no harm will be done
"95% of synthetics are about 50/50 of conventional oil and synthetic..."
That statement is not factual. If the bottle is labeled synthetic than it is 100% synthetic oil. If it is a blend, it will be marked as such.
If possible, do not mix oils as the additive packs are different. stick with what is in the crankcase unless it is an emergency and you have no choice.