I'm not very mechanical but I do like to top off my car's antifreeze when necessary. I was checking under the hood today and noticed two locations to add antifreeze. This is the first car I've owned with two fill locations. Can anyone explain the reason why to me? I've been using Prestone 50/50 prediluted antifreeze coolant to top off our 1999 Hyundai Elantra. Is there any reason not to use this for our Niro Phev? If so what product should I use instead? Again, I'm only bringing the level up to full on occasion when needed and since my Phev is only five months old I haven't needed to do so yet.