When talking about computers, NOTHING cools better than water. It is the benchmark everything else is measured against. It has a thermal coefficient of "1". Anything you add to water will negatively effect it's ability to absorb heat. Additives such as Water Wetter, Zerex and antifreeze with a "anti-foaming" ingredient will lessen the negative impact, but not improve heat absorption. In rare cases, at very high temps and pressure anti foaming agents will minutely improve the heat transfer of water, mixed with a heavy mix of glycol it will significantly improve heat transfer. Neither of these conditions will ever happen in a comp.

The trick is to add just enough additives to prevent galvanic corrosion and biological growth. And as little as possible to maintain heat transfer. Generally between 5 and 10 percent additives mixed with distilled water, and changed on a regular basis, is optimal.

I recommend the above mix for several reasons. One, it's cheap and readily available. Two, it's proven itself to work very well over several years of constant use and will not damage equipment. You can spend more money on high priced additives, but you won't be able to measure a significant difference over cheap antifreeze.