Yes, you can. It is even sold as a Synthetic Blend.
Yes.
It might be... It's highly not recommended to mix regular and synthetic oils.
yes
Yes, you can even mix them.
Yes, they even sell it that way.
Nothing happens, they just mix. You can buy "blended" motor oil.
Oil changes are always necessary. If you mean can you mix conventional oil and synthetic, the answer is yes you can.
Yes, you can even mix synthetic with conventional oil.
use it, it is ok to mix
That's okay.
Yes, you can even mix them.