[Royal Dutch]

Ok, I have read posts that state you must keep an eye on your coolant surge tank and add Dexcool 50/50 mix periodically because of either evaporation or under hot operating conditions you may lose some through the surge tank burping excess fluid.

My question is this, we know that water evaporates, do the chemicals that compose Dexcool evaporate also? I think not but am not a scientist. I have searched the internet for a definitive answer and have come up empty.

Assuming Dexcool does not evaporate, then only the 50% water is evaporating if your coolant level went down and you weren't at a track event/running your car hard in hot temps.

So, shouldn't we just be adding clean drinkable water/distilled water (my preference) to the lower surge tank to keep the levels in check? Otherwise if you are only losing water through evaporation and adding 50/50 Dexcool mix over time you will end up with much more Dexcool than water, not 50/50 mix per GMs recommendation.

Curious to hear what others think, if anyone has any real answers/data.

[N Camarolina]

I don't know exactly what chemical (besides water) is in Dexcool, but chemical compounds other than water actually do evaporate when exposed to air. Take alcohol (like 90% rubbing alcohol) for example. It not only evaporates, but it does so faster than water does.

At one point radiator coolant contained glycol (among other things), which is essentially an alcohol. So it's also possible that other components of Dexcool evaporate just as fast as the water does.

I wouldn't sweat the details here. Just refill with Dexcool if you are low. The amount (of what ever chemicals, including water) you are losing to evaporation is still small compared to the overall coolant volume in the system.

[Gunkk]

Based on what I could find, Dexcool contains ethylene glycol which can evaporate. If you are replacing coolant, you should use the 50-50 mix.

[Spaceme1117]

Originally Posted by Gunkk

Based on what I could find, Dexcool contains ethylene glycol which can evaporate. If you are replacing coolant, you should use the 50-50 mix.

That is incorrect. Boiling point of ethylene glycol is 197 C (387 F) and has a very low vapor pressure. So while it technically can evaporate an extremely small amount, you are losing mainly water if its from evaporation.

It won't hurt to top off the coolant system with 50/50 as it won't affect the water/glycol ratio much at all. But you could just top off with distilled/de-ionized water.

[OB0001]

top off with distilled water, should be fine