Auto Parts: Brake Fluid test is it Mineral or Synthetic, silicone brake fluid, fluid test

Question
How do I tell if fluid in a master cylinder is Mineral fluid or regular brake fluid?

Answer
    I don't know.  Mineral-based brake fluid (which means that it's made from petroleum) has a distinct taste, both DOT 3 and DOT 4.  However, it's also poisonous, so that's not the best way to tell.  There are more than one kind of synthetic fluid, as well.  If you are in doubt, and want something specific in your system, the best bet is to flush out the old and replace it with new.  Even with an advanced synthetic or silicone brake fluid this isn't going to cost much.