I’ve never understood why people buy 50/50 antifreeze (I’m not referring to anyone in this thread). I buy regular antifreeze and add my own water for two reasons. (1) I can adjust the engine coolant to be any concentration I desire, and (2) it is much cheaper to buy regular antifreeze.
I always do a flush (block, radiator, heater, etc.) when I do a coolant change. So, in theory anyway, all I have left in the system is water when I’m done. I don’t know how much is left, nor does it matter. I just check my owner’s manual for the coolant capacity and put in full strength antifreeze equal to 50% of the system’s capacity. Then I top it off with water to get my 50/50 solution. I use my tester after about a week to allow the contents of the reservoir to get thoroughly mixed into the system.
If you are after a 50/50 mix and do a flush and fill with 50/50 antifreeze you end up with something less than a 50% antifreeze solution because of the water left over in the system. The more water left in the system, the weaker the solution. So, how do you adjust it to get it back to 50/50? Well it’s easy…just add more antifreeze. But wait…all you bought is 50/50 mix…so that won’t work.
If you live in an area where freezing is not an issue, then as little as 30% antifreeze will provide the corrosion protection and a sufficient boiling point. If you live in an area that is subject to extreme cold, then you may need to run up to 70% antifreeze. Adjusting the mixture to get your desired weak or strong concentration is easily done with straight antifreeze, water, and some minor math.
As for cost, major brand antifreeze that is full strength sells for $17 at my local parts store. The 50/50 mix of the same brand is $15. So, that means that if I buy 2 gallons of 50/50 mix for my car then it would cost $30. Why would I do that when I could buy just one gallon of full strength antifreeze and add one gallon of tap water. If I am concerned about using tap water, then I could add one gallon of distilled water for $2. Let’s see…spend $30 or $19…oh, what to do, what to do? It just sounds to me like they are selling water for $15 a gallon.
Can someone fill me in on the attraction of 50/50 antifreeze?