Found some test strips that work with HOAT coolants.

Fleetguard CC8997. But you have to buy 25 strips and there is an expiration date.

Phoenix Systems 8001-B. You get 100 strips and apparently no expiration date.

HOWEVER it doesn't sound like there's one test strip that tells you everything you'd want to know (various inhibitors, etc.). The cost of an adequate test probably exceeds the cost of DIY changing the coolant.

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