Tap or distilled water w/ Dexcool?

[ProfPS]

I am planning to flush my '06 Malibu Maxx 3.5 cooling system and refill with Dexcool (still under extended warranty). What should I mix with Dexcool for a 50/50 mix: tap water or distilled water?

The owners manual and GM service instructions say to mix Dexcool with tap water, but I've always used distilled water to prevent mineral deposit buildup in the system. Will distilled water cause a corrosive situation?

 

[Johnny248]

Best off just buying the 50/50 mixed fluids. No chance of messing it up, plus you know it is mixed with a distilled and de-mineralization water.

 

[EricF]

distilled all the way.
distilled water has no impurities. it is as pure as water can get.
it won't be corrosive at all... however tap water has hard minerals in it and probably won't cause corrosiveness, but it'll allow scale to build up.

 

[ProfPS]

I agree with distilled water and green antifreeze. If Dexcool is designed to be mixed with tap water is it more corrosive if there are no minerals in the water?

 

[daman]

Yes for sure distilled water or RO.

 

[ekpolk]

RO? Reverse Osmosis? If so, where would you get that, other than a military ROPU?

 

[chet2]

go with distilled...i read a AF jug that said flush with distilled too, just run engine for 5 minutes

 

[chet2]

i have a pontiac and i am not using dexcool next time, not that i have had a problem with it

 

[The Critic]

Distilled.

However, it has been reported that straight OAT based coolants are less sensitive to water quality than coolants containing phosphates. This is why it is common to see phosphate-based coolants be sold in a premixed form, but not straight OAT coolants such as Dexcool or G-12.

 

[XCELERATIONRULES]

Distilled.
Why add who knows what minerals to an aluminum engine.

 

[daman]

Originally Posted By: ekpolk
RO? Reverse Osmosis? If so, where would you get that, other than a military ROPU?

Right Reverse Osmosis,i know distilled is better but if thats all one has it's better then hard well water.

WM sells it in bulk for like .39 a gal.

 

[ProfPS]

Picked up 2 gals of distilled at Walgreens - $0.69 ea. Which brand of Dexcool do you recommend? Probably will pick it up at WM - no Dexcool specials at AAP, AZ or NAPA.

 

[mechtech2]

Distilled water is cheap, and will be good for years in the car. The costs are therefore almost non existent.
It is the best first choice.
Some tap water is very 'hard', and some is 'soft'.
We have excellent Lake Michigan water around here, and I would have no problems using it.
But I repeat, distilled is best if you are positioned to get it. In many places or emergencies it is not an option.

 

[01rangerxl]

I always buy distilled water for my truck when I do coolant changes. For $1 a gallon or less, why not?

That said, one of my friends uses city tap water in his '95 Jeep YJ. It has never overheated and the coolant system is in good condition overall, though definitely not as clean as my truck's. We also just used regular tap water while flushing the cooling system on a badly neglected Cherokee, and I'm sure it will be fine, since tap water and universal coolant has to be better than mud.

 

[dailydriver]

Originally Posted By: ProfPS
Picked up 2 gals of distilled at Walgreens - $0.69 ea. Which brand of Dexcool do you recommend? Probably will pick it up at WM - no Dexcool specials at AAP, AZ or NAPA.


If your local NAPA can get it, I've heard that the Zerex Dex Cool is one of the best (IF there are actually any differences).
It was also about the same price as China Mart's Prestone D.C.

 

[onion]

I find it disturbing that somebody has to ASK this question.

Use distilled water. Or deionized water. Even though I do it to customers' vehicles every day- NEVER use tap water. Depending on you local water supply, there can be a huge amount of unwanted [censored] in it.

 

[Samilcar]

It's good to know what's in your local tap water supply. Mineral content is usually posted online for most municipal water providers. I have no problem using decent tap water that has been demineralized. If you don't know the content of your tap water, definitely don't take a chance, use distilled water. Distilled water isn't at all aggressive or corrosive towards any metal once it's been mixed with coolant.

 

[dailydriver]

Originally Posted By: onion
Use distilled water. Or deionized water.


The bolded above is what I've recently heard is the absolute best, but soooo many on here swear by distilled (and it IS 1000x easier to come by) that for the sake of peace I NEVER suggest it anymore.

 

[f2racer]

The distilled I recently bought at KMart had a best used by date on it... I don't remember ever seeing this before. Anybody know why?

 

[dailydriver]

Originally Posted By: f2racer
The distilled I recently bought at KMart had a best used by date on it... I don't remember ever seeing this before. Anybody know why?


Possibly it's there for the people who are going to use it for drinking water, and it warns of possible bacteria growth after that date??