Coolant...

[oj88]

I think we can agree to disagree on this.

But I'm going to nitpick the point about deionized water. Distilled water also lacks ions, and is purer with less contaminants than deionized water.

I want to be clear that I'm mainly against just putting in water (deionized, distilled, or tap - whatever the case may be) during top-up. Many owner's manuals details using 50/50 premix when topping up, so just adding water does imply that it will mess up the ratio and that's not a good thing.

I also read that distilled water's purity, and the lack of certain minerals, makes it unstable/unbalanced and can actually attack the cooling system (causing corrosion, scaling, etc.) The coolant solution still inside will no doubt take up most of the slack. But the irony there is, the supposedly "pure" water is actually using up and degrading the corrosion inhibitors.

But I understand if you disagree with that. Aside from Toyota, Honda also seems to use deionized water in their pre-mix. Some OEMs do use distilled water in their coolant pre-mix. But then again, I'm sure everything has been accounted for, chemically, and by pouring their coolant, you're maintaining the correct proportions.

For me it's just going to be Toyota SLLC so I don't have to worry about what's in it, nor its dosage.

My last Toyota was trouble-free for 9 years until I sold it, with the factory coolant still in it. I just top it off with a few milliliters of SLLC every 6 or so months if it dips below the Full line. I know I should've replaced it at year 5, but.... well, that's on me.