Do I add coolant or water to increase/decrease freeze and boiling points?

Hi,

This is a hard question to answer simply because I'm not sure what the ratio was that you installed already. The strongest mixture for engine coolant/anti-freeze is a 50/50 mixture.

Here is a link you may find of interest. It explains the general topics related to engine coolant.

https://www.2carpros.com/articles/engine-coolant-59420607

I hope this answers your question. If you added something other than a 50/50 mixture, compensate by adding what it takes to reach the 50/50 dilution.

Take care,

Joe