So you can help settle an argument for me. I bought one of those cheap $4 coolant/antifreeze hydrometer testers. The instructions say to make sure your engine is cool before you draw in the liquid. I said that this is only for safety reasons and that it wouldn’t impact the accuracy of the reading since it is testing for specific gravity. My friend says that the coolant can’t be hot or it will throw off the reading. I have asked two auto parts store guys and got the same two (different) answers. Checking online, - same thing …split decision.
So what is the real story? If the coolant temperature impacted the readings,then you’d get totally different readings if you tested it in the middle of winter when it is 20 degrees compared to a 100 degree hot summer day. That’s why I think it doesn’t matter if the coolant is hot or not - yet like I said…plenty of people and websites say the coolant has to be cold.