Tap Water or Distilled Water in your cooling system?

[OEM]

Do you use tap water or distilled water in your cooling system? I have a friend that REFUSES to use distilled water in his sytem because "it makes no difference."

Your thoughts?

[moso]

it makes no difference. the only use for distilled water on a vehicle that i know of is in serviceable batteries.

[allenms240]

No, it serves a greater purpose.

Tap water is often hard water (contains Calcium, iron, and other metal ions); it is not pure H2O and therefor contaminates your motor, water pump, heater core, and radiator. That's why it can get really dirty in older cars because people tend to use hose water.

Distilled water is de-ionized water, that is, there are NO ions in it except for hydrogen, and oxygen (H2O). It has no contaminants and that why people recommend using distilled over tap water.

I use tap water because, while it does contaminated the motor, I don't plan on keeping this motor forever. When I put in my fresh motor, I will most likely buy a new radiator and use distilled water to keep it clean.

[Dimitri]

I can see why tap water will be "preferred"; it's "free" and easy to get (just bring over the hose).
Distilled water, costs money AND you have to go to the store to get it.
After seeing how badly tap water scaled my coffee maker, I wouldn't want it anywhere inside my car
I buy the premixed coolant when I do a drain and refill. Never considered using "plain water"

[AZhitman]

it makes no difference. the only use for distilled water on a vehicle that i know of is in serviceable batteries.

Not true.

Ever seen an aluminum radiator with tap water after a year?

I run 80% distilled water, 15% coolant (not pre-mix, it's a ripoff), and 2 bottles of Water Wetter.

Using too much coolant is a waste of money as well. I've seen knuckleheads put an entire gallon in their radiator...

[IanS]

I run 80% distilled water, 15% coolant (not pre-mix, it's a ripoff), and 2 bottles of Water Wetter.

Using too much coolant is a waste of money as well. I've seen knuckleheads put an entire gallon in their radiator...

Wish I could do that. Stupid freezing weather.

Seriosuly, Distilled water is $0.98 a gallon at Cub. I have seen what tap water does to engines. Its cheap insurance.

[asoomal]

Tap.

Vancouver water ftw.