what does the bottle say, your purchased coolant is pre diluted (ready to use) ? or you need to mix with fresh water by 50 / 50 ratio
i have search out the forum and found toyota and caltex , zic to be top contendar
toyota is the best reviewed and long life coolant
first of you all you need to drain the radiator (previous coolant - unattach the pipes) , clear out the radiator with water and blow air in it
the radiator is clean , now close the drain pipes and pour coolant
it its pre diluted no water mix is required.
if its concentrated (not pre diluted) mix ratio of 50/50 in container first then pour in radiator.
complete method is explained by XULFIQAR BHAI @Xulfiqar
in this thread https://www.pakwheels.com/forums/air-conditioning-heating-ventilation/192808-how-change-coolant-radiator#post3376147
drain the radiator and measure how much came out, now open the thermostat housing to remove thermostat valve, push a blower nozzle in it and start the blower, it will push out all dirty water from the engine, measure what came out again. Write it down.
Put thermostat valve back, replace drain valve on radiator, add pure coolant to the engine, half of the quantity that came out, start engine and slowly add water, keep on adding until no more would go in, do not let it overflow, coolant is poisonous. Keep the engine running till the radiator fan starts, squeeze the rubber pipes to rid of any stuck air bubbles in the system. Once the system is stablized, put the cap back on, and observe any anomaly.