Oh ok, that's entirely up to you on adding it. Just be wise about adding things to your cooling system, some things don't like to mix well.

I should also mention that I have never done any research specifically on those coolant additives before. I've never really known anyone to use them, and the need to has not arose as of this point. I always thought that coolant had anti-corrosive properties because of what it's made from, and as long as you kept your fluid changed regularly it was unnecessary to use additives.

That does not mean that they are bad, just throwing that out there.

Most heavier plastics can resist temperatures up to several hundred degrees. If my memory serves me correctly, our engines run at like ~230 degrees at full operating temperature. That doesn't mean it would never melt, but your engine would literally have to be on fire and then you would have bigger problems at that point.

If it was just an overflow tank it wouldn't have a safety cap, and it would just be a vented "always open" cap like a lot of older cars have.


Just my two cents.