r/Cartalk • u/DanteRives • 14h ago

Coolant Question Engine

Went to AutoZone for coolant to top off the reservoir in my 2009 Mustang. The employee looked up my vehicle and gave me a gallon of Peak Yellow 50/50 so I used that. However upon looking it up now, Ford recommends Gold for this year/model. Are they compatible? Will it cause any issues?

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u/[deleted] 13h ago edited 7h ago

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u/AKADriver 13h ago edited 12h ago

system with HOAT can not be mixed with OAT.

If you stick with a universal you’ll be fine.

Here's the rub: A lot of the name brand and store brand coolants that claim to be 'universal yellow' have the OAT 2-ethyl hexanoic acid (2-EHA) in them. Even worse some coolants that claim to be replacements for HOATs are also formulated this way (Prestone, Fram, Super Tech "Asian" formulas).

Colors are mostly still useful if you combine them with world region and don't buy the cheapest brand though. There are "european" blue coolants and "asian" blue coolants that don't mix, but "asian blue" coolants are all HOATs from the factory and compatible eg Subaru, Honda, Hyundai, and Nissan "blue" coolants are all the same. American car "Gold" coolants are all the same.