While I don't use it in my PC loops, I do have a lot of experience with "anti-freeze" or "coolant" in actual automotive settings (road course racing, recreational and competitive as well as modifying BMW's).
It does not function just to prevent boiling of water (the fact that the loop is pressurized is a big factor in why it doesn't boil) or its freezing, it also serves as a very strong corrosion inhibitor, completely prevents any kind of growth, and is a very good lubricant for seals and the pump.
That said, it also DECREASES THE COOLING EFFICIENCY of water. Due to the fact that, in the event of a crash and leak, it doesn't evaporate and is a PITA to clean, it's banned from most racing circuits.
Most of us have always used just distilled water anyway, but once you're racing in events like the GT ALMS, you quickly realize that the very, very heavy, sustained loading of the entire car let alone the engine, necessitates a more efficient solution. That's where products like Redline Water Wetter come in. The fact is, under 12hr and 24hr endurance racing, I've seen water temps drop as much as 28*F thanks to Water Wetter, and consequently the oil temps dropped 11*F, the intake air charge dropped 19*F, the Lysholm twin-screw blower (I run @ 24.5 PSI for races where I'm allowed to use 109-111oct fuel) compressor output temp was 12*F lower, and the air exiting the Front Mount Intercooler (triple-thick core) went from 133*F to 105*F thanks to the complete elimination of heat soak in the engine bay. Lap times dropped from ~1:44.22 avg to ~1:38.56 on average, and I went from a 13th place start to a Podium finish. Dyno'd my car after the race, as usual, for comparison against the pre-race dyno....and it went from 538.9rwhp to 581.1rwhp strapped down, although accounting for the temp difference as it was 83F for the Before and 71F for the After, the overall horsepower difference was still over 30hp at the rear wheels, it remained flatter from the 6krpm to 9.5krpm sweet zone, and the torque curve began about 250rpm earlier at just 1085rpm and peaked faster hitting max at ~1455rpm and holding all 498.8lb-ft of torque at the rear wheels up through 5090rpm (this was a '05 330Ci ZHP fully race prepped; 2613lb total weight, custom fenders to fit 18x10.5" front and 18x11" rear wheels with 275(F) and 295(R) section width tires; straight cut six-speed, sintered iron/kevlar-cerametallic clutch and 6.8lb flywheel; fully built M54B30 with custom Lysholm twin-screw blower and front-mount intercooler; Quaife many-clutch variable locking limited slip diff; stripped interior with 19-point welded custom chromoly cage and a pair of Kevlar/Carbon Fiber Recaro race buckets with 6 to 9 point harness supports)...
IN A COMPUTER....
We're talking temps that are, in a good loop, no more than 3-7C above ambient, and in many loops (we'll say, "not so well planned out" or "insufficient radiator capacity" loops), it's between 10-20C above ambient. That's as hot as it gets! Far cry from 240C !!!!
You're FAR, FAR, FAR better off using:
1) Distilled Water from the Grocery Store
2) PT-Nuke/PT-Nuke PHN/Mayhem's XT1 in the proscribed quantity
3) Good tubing (currently only Primochill Advanced LRT is proving to be free of any plasticizer)
4) THE SAME METALS!!!
The worst things you can do are mixing metals, or putting junk in your loop haphazardly. I always recommend against Nickel Plated blocks (especially now that MIPS is out of business; theirs and Heatkiller's are the only ones I've never once seen an issue with; have had so many issues with EK that I simply don't buy from them nor would I ever recommend that you do), against using a Silver "Kill Coil" instead of or with a Biocide (especially if there's anything more than just copper/brass in your loop!) because not only is it less effective but it just adds an even greater Galvanic Index delta between metals, and I always recommend Bitspower and Monsoon fittings as never once have I seen them fail or lose their plating. Swiftech, EK, and Phobya fittings have all corroded easily, with random fittings from the first two companies actually being painted instead of anodized or electroplated and causing a huge mess.
The absolute BEST advice I can give you: DO NOT GET INTO WATER COOLING UNLESS YOU HAVE THE MONEY TO AFFORD TO DO IT RIGHT!! Otherwise, if you "cheap out", it will always end up costing you far more than if you just spent the extra up front for quality parts.
(BTW, the absolute best blocks come from Swiftech, XSPC, and Koolance for CPU's, and Heatkiller and Aquacomputer for GPU's; no competition, and stay away from EK! Aside from the many, many other issues, I lost TWO R7970 Lightning's to TWO SEPARATE EK Blocks that each had a different but equally fatal manufacturing defect as well as multiple "QC - Passed" stickers! EK never once responded to my emails, calls, or anything; thankfully, MSI replaced the 7970 Lightning's with 680 Lightning's so I could get the Aquacomputer Full-Coverage blocks, which are absolutely perfect; the Heatkiller Hole Edition 680 blocks on my 670 FTW 2Gb cards are the best I've used, weighing almost 2kg and made almost entirely from a single piece of milled copper)
