My MR2 still has some rust in the coolant after last week’s flush, so I’m looking at using Thermocure for a more comprehensive flush.

Should I invest in distilled water to go with this for the cleaning process, or will tap water be okay? Engine is an iron block, so I’m looking to make sure I don’t make the rust worse using the wrong water with this setup.

Also, any recommendations on coolant once the system’s clean?