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Q: De-ironized water or tap.

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I need to do a coolant change and I'm wondering if it's better to use deironized water mixed 50/50 with antifreeze or use tap water mixed 50/50 with antifreeze , some think it's better to use deironized water ?? Please help.

My car has 86000 miles.
My car has an automatic transmission.

You should not use tap water since it has added chlorine, calcium, and other additives that de-ionized water will not. You can purchase coolant already pre-mixed 50/50 or mix it yourself with de-ionized water and coolant mixed 50/50. You can also use distilled water if you cannot get or find de-ionized water.

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