Long life P-HOAT coolant, for asian cars. The key is it has to be silicate and borate free. I use valvoline xerex blue, it actually has a purple color, similar to the OEM coolant and specifically recommended for Hyundai. Some european formulations such as Pentosyn should work also. The valvo blue is a bit over $12 for a 50/50 premixed gallon.
But:the actual OEM coolant can be ordered on Amazon for $24. This is cheaper than it appears, because it is non-diluted. Have to dilute it with equal amount of distilled water before use, so really it is only $12 per gallon, about same price as the valvo.
Robot Check
Obviously, you cant go very wrong with the genuine Hyundai coolant.

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Using the right coolant is fairly important, it depends on things like: do you have led solder in your radiator? Is it aluminium? Is it copper? etc. Over time you can have problems if you just use an inexpensive generic short life green coolant. The generic coolant packaging will tell you it can be mixed with any other coolant... Not.