is using not diluted coolant harmful

Get manual and find out radiator capacity. Any chance it's 2 gallons?

I think 85/15 should not be dangerously harmful in the short term but it will not cool as well because ethylene glycol has lower heat capacity than water. On the other hand, 85/15 mix won't freeze well into -50C :-)

DK

just checked the manual - it is 7.1 qt, so my worries are gone.

I somehow misread it before and thought it is 5.1qt.

thx, A.

Isn't the lowest freezing temperature for an ethylene glycol and water mixture -84F -64C at about 70% concentration?

One problem in general is that ethylene glycol is more viscous than water. Not only does it have lower specific heat but it's not going to flow through the cooling system as quickly.

My number was pure guesstimate - I just knew it's gotta be below -50C :-) I don't think ethylene glycol at 85% will freeze at higher temp than 70% would, but that difference is pretty irrelevant here. (Although, to think of it, if the miscibility of EG and H2O decreases significantly with temp, I can imagine that at sufficiently low temp you could get water islands nucleating and triggering freeze at lower temperature; maybe).

Certainly, that too. It's also denser.

DK

I'm having a hard time finding an actual chart of ethylene glycol/water mixtures and freezing temps other than bottles of antifreeze that stop at 70%. The freezing temp of pure ethylene glycol is supposedly higher than even a 50/50 mixture with water.

It's one of those strange things where mixing it with water creates an effect that lowers the freezing temp to below that of either alone. The following states that maximum freeze protection is at 67% ethylene glycol (-84 deg F) and pure ethylene glycol freezes at 8 deg F.

I'm not sure what it would be at 85%, but I don't think it's terribly beneficial. I would try to get the concentration down to about 50% if it were my car. I don't really encounter anything lower than subzero temps even when I head for the mountains. I'm generally more worried about cooling.

since you guys are talking about AF, I heard that the ph of it should be checked twice a year, so acids don't eat up plastic parts. I also heard that 10% will keep the coolant from freezing solid, and just turn to slush. I have no idea what % I have. I was changing mine, and found mineral deposits in the upper tubes of my Chevy, and had a small leak in the radiator. I rodded out the tubes, and put in stop leak till I could solder the leak, and haven't gotten back to it. I am disabled, and it has been a Few yrs. I probably tested it, but can't remember. It is green, and hasn't had a problem. Though one time the leak opened. It probably slushed up, and disturbed the stop leak.)

VF

Hi,

Years ago, it seems most antifreeze jugs had a little chart on the back...

From memory, about a 70% concentration produced the lowest freezing temp, as well as the highest boiling temp. Above 70%, both numbers actually started getting worse.

The boiling temp difference between a 50% and a 70% concentration is not really that significant (maybe 10-11 def F?), and even if one were to overheat enough to boil a 50% mix, most of today's engines would already be damaged. For those who live in truly hot climes, it's interesting to note that pure water actually cools BETTER than a heavy coolant mix, so a 10% solution is sometimes recommended simply for corrosion protection.

I've also heard, though I can't verify it, that while ethylene glycol in combo w/ water protects against corrosion, in 100% concentration, it's actually corrosive (one of the reasons it's not recommended in engines.) Anyone have any info in that department?

Rick

Just looked at the chart on my coolant jug. It only goes to

70% of the concentrate with corresponding freezing point

-84F/64C

Hmm, could be, for ethylene glycol. Although it's definitely not true for alcohols - freezing point of 100% ethanol is lower than any of its aqueous solutions.

No, ethylene glycol by itself is not corrosive at all. But pure ethylene glycol is hygroscopic and usually ends up with some water. High EG concentration + some water + heat = acid production. Acids are corrosive. And acidic pH promotes formation of more acid. That's why commercial coolants contain pH buffers. I'd imagine if your coolant, diluted 10X with pure water, give pH >7.5, there is nothing to worry. If it gives pH < 7.0, it's probably a good idea to change it ASAP.

DK

I think that's approximate. The link I had from Peak Antifreeze stated 67% was the ideal concentration for lowest temperature freeze protection, at -84 deg F.

I knew someone who bought some vodka and chilled it in the freezer. I've tried it myself and darn it if it didn't freeze over. Made for a very cool shot.

I believe at least one of the two major organic acid corrosion inhibitors serves as an alkaline buffer.

Supposedly straight propylene glycol won't freeze over, but will just turn to slush. I've heard of a few 100% propylene glycol cooling systems.