BMW coolant -- distilled or tap water?

[dparm]

Finally changing out the coolant in my M3 since it just ticked 50k. BMW claims it's lifetime but I call [censored] on that.

The OEM concentrate bottles don't say you need to use distilled water, but they also don't say to avoid tap water. It is a phosphate-free fluid so in theory there is no benefit to using tap water.

Does anyone know what BMW recommends in this regard? The dealer was of no help: "well it's lifetime so you shouldn't have to change it out".

 

[95busa]

Cant go wrong with distilled and its cheap.

 

[dparm]

Originally Posted By: 95busa
Cant go wrong with distilled and its cheap.


But tap water is cheaper.

My question is more around the chemistry and coolant additives, and if they're most effective with a particular type of water.

 

[antiqueshell]

My guess is that the 50/50 version of that BMW coolant you can also buy at the dealer, is pre-mixed with distilled water, so go with that.

 

[Quattro Pete]

My mechanic said distilled, but didn't really explain why. I guess it's just cleaner. Tap water may have some sediments that may deposit themselves inside your cooling system when exposed to heat, alas, I can't imagine there's going to be a lot of sediments in tap drinking water to begin with.

 

[Astro14]

Distilled water around here is 69 cents/gallon at the grocery store.

So, you're going to take a chance with your BMW over less than the price of a small coffee at Starbucks?

OK....

 

[kschachn]

You can buy 50/50 BMW coolant? I have never seen that at the dealer. What color is it?

Originally Posted By: antiqueshell
My guess is that the 50/50 version of that BMW coolant you can also buy at the dealer, is pre-mixed with distilled water, so go with that.

 

[kschachn]

Yes, distilled water.

I'm still struggling with the idea that you have a newish BMW and you actually are thinking of saving $2 by using tap water.

Originally Posted By: dparm
My question is more around the chemistry and coolant additives, and if they're most effective with a particular type of water.

 

[dparm]

Originally Posted By: antiqueshell
My guess is that the 50/50 version of that BMW coolant you can also buy at the dealer, is pre-mixed with distilled water, so go with that.


BMW doesn't sell it pre-mixed. Concentrate only.

And yes, I know distilled is cheaper -- again, my question is about whether or not certain types of coolant actually need tap water to work better. Certain corrosion inhibitors need somewhat-hard water to properly activate.

 

[kschachn]

They do? Where did you read that? How much hardness? When I lived in the City of Milwaukee and we got lake water, it was of extremely low hardness. Are you suggesting that wouldn't have worked?

Originally Posted By: dparm
BMW doesn't sell it pre-mixedAnd yes, I know distilled is cheaper -- again, my question is about whether or not certain types of coolant actually need tap water to work better. Certain corrosion inhibitors need somewhat-hard water to properly activate.

 

[SF0059]

Tap water contains many elemental impurities including trace iron, sulphur, sodium, calcium, and copper. Depending on the water table where you live some may be higher than others. Given that variable, distilled water is always preferable, especially if you live in an area with hard water or have galvanized piping in your home.

Imagine the hard water ring in your toilet or sink in your coolant system. This is why distilled is always better.

 

[dparm]

Originally Posted By: kschachn
They do? Where did you read that? How much hardness? When I lived in the City of Milwaukee and we got lake water, it was of extremely low hardness. Are you suggesting that wouldn't have worked?

Originally Posted By: dparm
BMW doesn't sell it pre-mixedAnd yes, I know distilled is cheaper -- again, my question is about whether or not certain types of coolant actually need tap water to work better. Certain corrosion inhibitors need somewhat-hard water to properly activate.



I was just at the dealer and bought some. Asked the parts guy if it comes pre-mixed and he said no, but the techs have the special hoses that dispense it at 50/50. This isn't an issue of cost.

The reason I know about how the corrosion inhibitors work is because my brother is a chemist specializing in water treatment.

 

[kschachn]

Well, I have a minor in Chemistry, that is why I asked. I know some things about chelating agents and sequestering and I had never heard of that.

So you are still maintaining that when I used water from the tap in Milwaukee that was not as good as the well water here in the suburbs?

Originally Posted By: dparm
The reason I know about how the corrosion inhibitors work is because my brother is a chemist specializing in water treatment.

 

[fdcg27]

If you have really bad water from a well, it might matter, but if you're on a municipal water system, I doubt that it would.
If you'd feel better using it, pick up a gallon of distilled water for a little bit of nothing.
I don't think that there'd be any practical difference, though.
The coolant will soon be full of minor trace impurities from every surface it comes into contact with.

 

[dparm]

Originally Posted By: kschachn
Well, I have a minor in Chemistry, that is why I asked. I know some things about chelating agents and sequestering and I had never heard of that.

So you are still maintaining that when I used water from the tap in Milwaukee that was not as good as the well water here in the suburbs?

Originally Posted By: dparm
The reason I know about how the corrosion inhibitors work is because my brother is a chemist specializing in water treatment.

I suspect my brother was over-simplifying since I barely passed chemistry in high school.

His comment about phosphates stuck out, so I'll probably stick with distilled water.

 

[Kira]

Hello, 4 examples with no empiricism.
1) Well maintained' 99 Saab with Saab blue (G-46?) coolant.
Drained, cleansed and rinsed finally with distilled water. G-05 refill
Sparkling to this day.
2) 2005 Saab with DEX-COOL to which green had been added.
Drained, cleansed and rinsed finally with distilled water. DEX-COOL refill
Sparkling to this day.
3) Neglected 1997 F-150 likely running factory fill.
Drained, cleansed 3 times, rinsed beyond sparkling with a trickle of extremely hard well water for over 2 hours. Green refill
Looks dull already
4) Neglected 2003 S-10 running rusty DEX-COOL.
Drained, cleansed twice, rinsed to clear with municipal (New Milford, CT). DEX-COOL refill
Getting dull
Go for distilled water. Don't be selectively naive. Kira

 

[BISCUT]

Originally Posted By: kschachn
You can buy 50/50 BMW coolant? I have never seen that at the dealer. What color is it?

Originally Posted By: antiqueshell
My guess is that the 50/50 version of that BMW coolant you can also buy at the dealer, is pre-mixed with distilled water, so go with that.


I just went throught his with my 08 last week. I was told the only coolant that applied to my 08 3series was the blue BMS and only came offered in full strength. Distilled always the way to go.

Mine is I6 and took 1 and 3/4 gallon.

 

[JHZR2]

For the $1-2 in distilled water it will take, that's a no brainer.

 

[michaelluscher]

Distilled.

 

[raytseng]

Originally Posted By: dparm
Originally Posted By: antiqueshell
My guess is that the 50/50 version of that BMW coolant you can also buy at the dealer, is pre-mixed with distilled water, so go with that.


BMW doesn't sell it pre-mixed. Concentrate only.

And yes, I know distilled is cheaper -- again, my question is about whether or not certain types of coolant actually need tap water to work better. Certain corrosion inhibitors need somewhat-hard water to properly activate.


This doesn't make sense. If it needs something else, it should've been in the concentrate.

Germans wouldn't think that way. If they say requires H2o, they are expecting exactly 100% h2o.
Not h2o plus some unscientific magic fairy dust that comes from tap water.
Or they would've sold you extra calcium or whatever as an additive to use when using 100% h2o.