Many new cars come over filled or underfilled from factory, sometimes there's a pocket of air in radiator which clears up when vehicle is used and coolant is sucked from reservoir to compensate.
E.g. my Altis 1.6 is slightly underfilled while a friend's fortuner was quite overfilled.
I'd say if u need to top it up slighly, do it with distilled water as antirust properties aren't affected by slight dilution
if u need to fill more than half a liter, buy caltax concentrate and add distilled water to make a 50-50 mix.
Distilled water can also be used to top up battery if needed and it's usually sold as battery tonic.
