Never use Ethylene Glycol (car antifreeze) in a boat. First, if you spill it on the ground it can kill animals and children who will drink it because it tastes sweet. Second you can get a hefty fine for discharging it in the water OR on the ground.
Use marine antifreeze on raw water cooled engines (or the raw water side of a closed cooling system) if you must use antifreeze. A closed cooling system (I/O or Inboard) is different in that ethylene glycol is used on the closed side (like an automobile) and marine antifreeze is used for winterizing the raw water side.
I say marine antifreeze because it has the water pump lubricant and anti-corrosive ingredients already in it and it's non-toxic. Do not take RV anti-freeze and add automotive water pump lubricant and anti-corrosive ingredients because you will then make it toxic. The marine anti-freeze comes in three flavors: -50F, -60F and -100F. Remember, that is the freeze solid temperatures. It will turn to slush before that (which is harmless). Do check the label for the temperature it will protect PVC since that will be less.
Remember, air won't freeze. If you follow your manufacturers recommendation and drain all the drain points there will not be any water in your system to freeze. Make sure all drains are clear by using a coat hanger to clear them. You CAN backfill with anti-freeze after you drain if you wish. You only need to stand an O/B straight up to drain it and don't need anti-freeze.