Antifreeze for the Kia Optima and K5
The Optima and the K5 are the same car under different market names. In Georgia it often works a hard daily routine, sometimes as a taxi. Valvoline Zerex Asian Blue is an approved formulation for MS591-08.
Photographs come from the manufacturer's official materials.
Cooling system volume (litres) roughly six to seven litres
Mileage does not tell the whole story
Service intervals are usually written in kilometres, but for coolant what matters more is time, and how many hours the engine actually runs.
A car working in the city spends many hours a day idling or crawling in traffic, where the odometer barely moves while the engine runs and heats up. On that duty cycle the fluid ages faster than it would over the same distance on a motorway.
So on an Optima in daily use, do not run the five-year interval to its end. Four years is the more sensible mark.
The Optima Hybrid
The hybrid version has a separate cooling circuit for the power electronics, with its own reservoir and pump. Its fluid ages just as the engine circuit's does, only almost nobody checks it.
If there are two expansion tanks under the bonnet, the second one belongs to the inverter. Check its level periodically and leave the fluid change to a specialist.