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Thread: Coolant Testing

  1. #1
    Senior Member Citizen's Avatar
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    Location:  Houston, TX

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    Coolant Testing

    A number of months ago, my family had the sad task of going through my brotherís garage after he passed away. Of course we found a lot of good, usable stuff like tools & supplies. We also found 4 gallons of antifreeze. Two gallons were unopened and were 100% antifreeze (Prestone). The other two gallons were opened, but clearly never used, one was 100%, the other 50/50. And these are known to be at least 12 years old plus (donít ask how I know, itís just one of those family things).

    The question for the classic car community is, is NOS antifreeze this old still good? Iíd like to use the stuff in my other daily drivers or my other classic car rather than throw 4 gallons of antifreeze away (or take it to a recycle place). Thing is, for example, my 2005 Chevy Colorado owners manual suggests to use only DEX-Cool at 50/50 strength, and suggested mileage change is 150k miles (only has 65k miles on it). None of the NOS antifreeze is DEX-Cool stuff. Also, my classic car just had an antifreeze change about 2 years ago, and has probably under 1000 miles on it since.

    Hereís where I need advice from you pros: Should I never use this old, classic anti-freeze, and should I recycle it? Or is it ok to use in some of my other cars? I also have a 2008 tractor (a diesel) which could use a coolant change, but I tested it and it protected down to about zero deg. F (see below how I tested it).

    Since weíre on the subject of coolant, to do the testing I bought one of those cheap glass-dropper antifreeze testers, with the five colored balls inside, that when a number of them float (or not), it gives you an indication of how well you are protected from freezing/boiling. Hereís a picture of the tester:


    According to the directions, the number of balls floating indicate: 1 ball: protected from freezing down to +20 deg., 2 balls:+5, 3 balls:-10, 4 balls:-25 and 5 balls:-40. It also lists the boiling points as: 1 ball:+215, 2 balls:+218, 3 balls:+222, 4 balls:+225 and 5 balls:+228.

    When I tested my classic, it showed 2 balls floating (protected down to +5 degrees. I live in SE Texas, and it rarely freezes here. I think the lowest it has ever gotten was +20 or +18, so Iím not too worried about a freeze-up. My Colorado had 4 balls floating (down to -25 degrees), so Iím not too worried about it, except that the antifreeze in it is old as well.

    The opened jug of 50/50 antifreeze tested at 5-balls floating (-40F deg.).

    What does everyone recommend as far as using the old antifreeze, or tossing it?

    Thanks in advance,

    Keeper of the DeLorean Owners Directory, at

  2. #2
    Senior Member Rich's Avatar
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    I'd use it. Ethylene glycol is very stable.

    See linked article on this topic:

    And when it comes to testing what's in the system I like using these strips:

    Not only do they tell you the freeze protection level of your mixture they tell you its pH.
    March '81, 5-speed, black interior

  3. #3
    Administrator Ron's Avatar
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    Someone probably poured some pure into the 50/50 = -35į lowering it to -40į F.

    DEX-Cool is 5 year/150,000 and doesn't mix well with other antifreeze (may gel after time...), but you can use it if nothing else is available.

  4. #4
    Delorean Guru
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    If you don't see any sediment on the bottom of the bottle it is still good. A much more accurate way to test is with a diffraction scope but the floating balls is close enough to tel you if has been mixed or not. The Ethelyn Glycol is very stable but the additive package is not.
    David Teitelbaum

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