Yes you can mix different brands but I recommend you do not mix different weights. You can even mix synthetic oil with conventional oil. But as the weight of the oil is critical, do not ever mix one weight of oil with another, no matter if it is synthetic or conventional oil.
Unlikely
When it comes to cars, oil and water don't mix. Oil has its own reservoir as does water.
Yes, it is fine to mix brands.
Nothing if they were approved oils. You can mix 10w30 with 5w20 etc. Not a good idea but you can do it. You can mix brands with no problem.
When mixing 2 stroke oil , the oil to gas ratio should be on the bottle . Different brands of oil mix different . But the bottle should tell you how much oil to gas to get the 32-1 mix that you want .
Yes, as long as they are both oil based or both water based.
From what I was taught, yes. Keep in mind this does have an effect on the additives mixture. I would really recommend sticking with one brand per oil change however.
Oil and oil will mix.
No , if you start the engine than the oil and coolant will mix and it will also be in the oil filter
usually motor oil and a sugar mix
That's okay.