Automobile Enthusiasts

When adding engine coolants to a vehicle, its important to know exactly what coolant is in the engine.

There are several different types:

-Inorganic Additive Technology (IAT)
-Organic Acid Technology (OAT)
-Hybrid Organic Acid Technology (HOAT)
-Phosphate-Free HOAT
-Phosphated HOAT
-Silicated HOAT

If you're dealing with a coolant leak and do not know the type of coolant is in a vehicle's engine, the safest play is to add Distilled water. DO NOT add tap water or filtered well water, as chemicals and minerals in tap and well water (especially municipal system supplied water) may react poorly with whatever coolant remains in the engine.

If you're changing out coolant or adding coolant to an engine with no leaks and you've purchased a gallon of undiluted OAT coolant, cut this undiluted coolant 50/50 with Distilled water BEFORE adding it to the cooling system.

https://www.valvolineglobal.com/en-eur/what-happens-when-you-mix-coolants/