What is the best water-cooling coolant?

Fluid XP+ Ultra

Manufacturer: Fluid XP+
UK price (as reviewed): £14.51 (inc VAT)
US price (as reviewed): $19.98 (ex TAX)

With a claimed boiling point of 340°F and freezing point of -50°F, there's clearly something interesting going on with FluidXP+'s Ultra coolant. According to FluidXP+, this has something to do with the various compounds used in its formation, including one called z-7, which supposedly also reduces gunge buildup (mainly from particles from the inside of tubing, blocks and radiators detaching and entering the coolant flow) thanks to what sounds like a form of encapsulation.

This apparently prevents particles then attaching elsewhere in the loop, and allows it to maintain a degree of non-conductivity longer than any other coolants, according to FluidXP+.

It's a clear coolant out of the bottle, but the company says it's fine to combine it with dyes and water, the latter apparently increasing thermal transfer properties (we take it all the fancy features actually come at a cost then...). It also smells slightly of chemicals, but as we weren't there to smell-test each coolant, this didn't worry us. What did worry us, was the price - at nearly £15, this is expensive stuff, and sadly, the advantages in showed over the competition (mainly in flow rate), was insignificant.

With an absence of long-term testing for gunge build-up and the like, which is sadly, not possible without spending months testing and filling our lab with water-cooling gear, it's difficult to see why you should spend nearly triple the amount as you would with Nanoxia's Hyperzero, which costs just £6. There are those of us who have tried and tested simple deionised water and additives for long periods with no ill-effects too, meaning that if you're after a simple, clear coolant, FluidXP+ is an expensive way to go.

Mayhem's Aurora Tharsis

Manufacturer: Mayhem's
UK price (as reviewed): £15.49 (inc VAT)
US price (as reviewed): $20.99 (ex TAX)

Relatively new to the water-cooling scene is UK-based company Mayhem's, which has been experimenting with a variety of coolant mixes recently. Our experience of its Mayhem's Pre-Mix X1 UV Red wasn't amazing - it had little UV effect but did look very red and kept up with all the other coolants in our flow rate and temperature tests.

Mayhem's also offers pastel and pearlescent coolants too, and its Aurora range, of which the Tharsis red coolant we're looking at here, has what Mayhem's describes as a suspended nano silver pearl effect.

This translates into the coolant having a swirling, pearlescent finish, but despite our initial concerns that the effect wouldn't look quite as great on the move as it does static, we can honestly say that this is one of the most downright awesome-looking coolants we've ever seen, even at maximum flow rates.

As a bonus, we didn't notice any drop off in performance compared to other coolants in our test system - in the real world, in a real PC water-cooling loop, this stuff appears to work just as well as the competition. At £15, it's not cheap, though, and sadly, Mayhems also stipulates that the Aurora series shouldn't be used for long periods in your system, instead as a short term bout of eye candy (see more on this here). However this water-cooling game is now just as much (if not more) about looks than it is about performance, and this is awesome stuff to add to your system, even on a short term basis for your final project photos, LAN party or modding event.

Just when we thought coolant was getting boring, Mayhem's has taken a giant leap on the back of some sound testing and research and for less than the price of handful of compression fittings, you can add this extraordinary stuff to your loop for some ultimate swirling pimpage, that looks just as good in clear tubing as it does in a reservoir. Just remember it's only for short term use.