Any time is a good time to test your coolant but most important is when winter months are approaching. I know that there are many other articles on how to check your engines coolant for the proper mixture. I am not saying that any of these methods are incorrect.
I am going to discuss a method in this article, which I find to be the most accurate method possible. The problem with some of the other methods such as the floating ball method is that there are many different kinds of coolants out there. This means that you have to have the exact tester for those coolants to make the gauge read accurately. Sometimes you may also be unsure what type of coolant is in the vehicle, and you then don’t know what tester to use. This can also lead to using an incorrect tester and getting incorrect reading that either say your coolant is the correct mixture when it is not, or else saying it needs more antifreeze when it does not.
The method this article is going to focus on is using a refractometer. A refractometer, such as this ATD3705 Coolant Refractometer or Robinair 75240 I have found to be the most versatile, accurate and economical way of checking cooling systems.