The system on the Tucson should be checked when dead cold/before starting it that day. The level will move around when the engine is running/depending on how hot, etc it is at the time.

Mine needed a tiny bit of distilled water when brand new to bring it from min to max when cold. It didn't take the full 8oz from the bottle I use when I travel with my cpap.

Over the next year and a few months. I added another 6ish oz of water to bring it back when cold.

Critical? Probably not, but I am weird about keeping things to max (more time to notice a leak before the fluid is gone is my best logic on that). No signs of any issues other than the water is likely evaporating a bit to cause that. Note: The book says to add distilled water and not 50/50. Why (of anyone who asked that) if it is evaporative loss, it loses water and not coolant. Especially on the coast where I am - it stays a bit stupid warm.

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sooo... I'd keep an eye on it for a bit when it is cold and track where the level is under that condition to see if you actually have an issue or not. If its a hybrid. Some eat it via a heat exchanger (??) in the exhaust. Never going to see the leak there.

 

As per the owners manual, the coolant reservoir should be filled to between MIN and MAX when the engine is cool.

If you fill it to MAX when the engine is cool, and then check it again when the engine is hot, it will likely be over the MAX line. But when the engine cools, it will be siphoned back into the radiator.

 

Always check with engine off and "cool" (ie parked overnight) though this time "cool" was mid heat wave.

Anyway my records indicate I've topped up the fluid 4 times. each time from "min" to "max", I don't think this is a huge quantity each time, but starting to add up.

The dealer did it each time, each time I told the dealer to check & topup the fluid level, each time they did not, each time I complained, each time they did it right in front of me after that, each time it was with coolant, not distilled water.

So if its an "evaporative" loss, my coolant is getting more concentrated. Never thought about wether it should be topped up with coolant or distilled water. On the other hand if it is being lost to leakage or consumed in some way, then water would slowly dilute it.

Also the car was initially delivered at "low". Yesterday at the dealership, the car in the showroom also had its coolant level at "low".

 

Keep in mind that this is a pressurized system. Heat generates expansion and increases pressure. If it exceeds the maximum pressure value, it is released until it stabilizes.
A maximum level, or close to it, in cold conditions is not the best choice.
Excess pressure is released, and with it, part of the coolant.
By adding water, we reduce the boiling point of the coolant, causing the level to drop further due to evaporation.
Therefore my experience have shown that coolant level between MIN and MAX is advisable at average engine working temperature, that leaves enought space for coolant to expand without evaporation