In the owner's manual for my 2001 Ford F-150 (5.4L), in the section on "Adding engine coolant", it specifies the type of coolant to be used, and says it should be mixed 50/50 with distilled water. It explains how to open the coolant reservoir and so forth, and then there is the following paragraph (emphasis mine):
After any coolant has been added, run the engine for a few minutes to mix the coolant. Check the coolant concentration. Make sure the engine is off and cool before removing the coolant pressure relief cap (see proceeding [sic] steps on cap removal). Check the concentration per the Checking Engine Coolant section. If the concentration is not 50/50 (protection to -34 F / -36 C), drain some coolant and adjust the concentration. It may take several drains and additions to obtain a 50/50 coolant concentration.
The section on "Checking Engine Coolant" explains how to check the level of fluid in the coolant system, but in an apparent omission, does not actually say anything about how to check the concentration. I don't know how one would do that.
Short of a complete chemistry lab, is there actually a way to test the concentration of coolant in the system, to see whether it is 50/50 as specified?
Other than by somebody having added the wrong concentration, is there any reason why the concentration of coolant currently in the truck should become incorrect? Why would it be necessary to test it? (Differential evaporation rates, maybe?)
It seems like the question Is coolant testing necessary on modern vehicles? is also about some method of testing the coolant mix that's already in the vehicle. But I don't really understand what they are talking about, and it doesn't directly address my questions.