There seems to be some confusion between HOAT and OAT coolants. 2008-2012 Challengers use HOAT coolant. From 2013 to the present, all Challengers use OAT coolant. Here is an explanation on how these coolants differ: Hybrid organic additive technology (HOAT) which is orange in color. Manufactured for NAFTA, it uses a combination of organic additives (fully neutralized organic acids) and one or more inorganic materials; uses silicates as the fast acting anti-corrosion agent – FCA HOAT (MS-9769). It last for 5 years or 102,000 miles, whichever comes first. HOAT-based antifreezes also contain an OAT additive package, plus an additional dose of silicates.The silicates are fast-acting chemicals that form a protective coating on aluminum surfaces. However, as the coolant ages, some of the silicates may drop out of solution.These particles can have an abrasive effect as they circulate in the cooling system, accelerating wear on water pump seals and plastic impellers, plastic radiator end tanks or inside metal heater cores with sharply curved tubes. To avoid these kinds of problems, most HOAT-based antifreezes use stabilizers to keep the silicates in solution, and they contain only a small amount of silicates. • Organic additive technology (OAT) the factory fill on FCA products is purple in color – Contains only organic components, no inorganic materials – FCA OAT (MS-12106). It is a "permanent" coolant and lasts for 10 years or 150,000 miles, whichever comes first. OAT-based antifreeze uses chemicals such as carboxylate, sebacate and 2-EHA (ethylhexanoic acid) to prevent corrosion. Antifreeze manufacturers won’t reveal the exact makeup of their OAT additive packages because they are proprietary secrets. But the chemicals are typically slow-acting so they can neutralize corrosion inside the engine, radiator and cooling system over a long period of time. Caution: OAT coolant is not compatible with HOAT coolant - do not mix them!!! The corrosion inhibitors are different and can cause long term corrosion problems if mixed. Other Cautions: There are several different OAT coolants available today, however they are not necessarily compatible. Using the correct coolant and water mixture is important for effective cooling. The recommended coolant mixture for most climates is 50% distilled or de-ionized water with 50% coolant. Do not use water with a high mineral content because: • The inhibitors in the coolant can lose their efficiency and lower the coolant’s useful life. • In addition, deposits can form inside the cooling system. These deposits reduce the ability of the cooling system to transfer heat. A 50/50 mix of ethylene glycol and distilled or de-ionized water provides the best mixture to prevent corrosion and obtains a freeze point of -37°C (-34°F). Note: Never use HOAT coolant with a concentration greater than 60% coolant and 40% distilled water.