Various names are used to describe this group of products: organic acid technology (OAT), silicate-free coolants, long-life or fill for life and also type D-coolants.
An organic additive technology (OAT) coolant contains only organic corrosion inhibitors such as carboxylates and triazole.
The carboxylate acid inhibitors used in OAT coolants have very low depletion rates. A monomolecular layer of inhibitors is formed on the metal surface only at the anodic sites where corrosion risks to start. These virtually non-depleting corrosion inhibitors give OAT coolants an extended life which can often be for the lifetime of the engine or vehicle.