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  #1  
Old 08-17-2002, 01:52 PM
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antifreeze question

This is got me bugged. If I mix 50% AF/water (ethylene glycol type) and test it with my gauge it gives me a reading off the gauge instead of the -34 deg F freezing point it should. This is true with 3 different gauges. To get a reading of a freezing point of -34 deg F, I have to add more water to the mix, bringing up to about 70% water. What gives?

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Old 08-17-2002, 02:14 PM
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Location: Evansville, Indiana
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Ethylene glycol or propylene glycol? The newer antifreezes use proplylene glycol, and the density is different -- the quick guages are density measuring devices, so if the density is different, the guage reads wrong.

I will check, I have a Merck Index somewhere around here.

Peter
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Old 08-17-2002, 06:35 PM
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Thanks for your response. I knew that. I have tested two antifreezes Prestone and Shell Rotella both ethylene glycol base with 2 different pointer type gauges. One is a prestone gauge the other NAPA, both say on the gauge, "for all ethylene glycol antifreezes." I get the same result. If I mix 50/50 they read off the top of the gauge. I can only get freezing point reading of -34deg F by adding a lot more water. Is there anyone out there who has done this simple experiment? The bottom line question is, can you trust these gauges? I don't think so.
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Old 08-17-2002, 08:24 PM
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Now this is interesting. I went out and bought some fresh prestone antifreeze mixed it with half water and it tests ok. So I have come to an entirely different set of conclusions (1) if you leave antifreeze laying around for a year even if it is capped the water in it evaporates and (2) Shell Rotella ELC premixed antifreeze is not 50/50 like it says on the container. So I learned always buy fresh stuff and don't believe everything that you read on a label. I'm ok now, thanks.
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Old 08-17-2002, 10:19 PM
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Are you fellers taking the readings at

the temperatures specified on the guages??? On the ones that I have (one cheapy Prestone and one very fancy professional type), it makes a huge difference whether you test the antifreeze at ambient temperature or at, for instance 190 degrees F., and I have seen neighbors coming to me for help because they took a cold reading and got exactly the confusing results you describe, because they were looking at the 180-190 side of the guage.
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Old 08-18-2002, 11:19 AM
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I got to the point where I placed my antifreeze meter in the trash about 5 years ago. The thing is a density meter and works well only for the brand that sells it, and in the same era.

Now I just drain the radiator and block, flush with water until it comes out clear, then refill according to the bottle label. Extra gets put in the trunk, after marking the % on the top of the bottle with a magic marker.

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