Distilled water paired with a corrosion inhibitor additive is the budget-friendly, no-frills approach, and it is what a lot of experienced builders default to for its simplicity and low cost per fill. The tradeoff is that you are responsible for getting the additive ratio right and monitoring for biological growth over time.

Pre-mixed coolants, like our ModWater line, trade a slightly higher cost for consistency. Every bottle is formulated the same way, so you are not guessing at ratios, and most pre-mixed options include UV coloring and biocides already balanced in.

Neither option meaningfully outperforms the other on cooling. Choose based on how much fine-tuning you want to do versus how much you would rather just pour and go.