Reposted reply to your original Q: Well there's the exotic stuff like novec and flourinert... but there may be glycol-based/other waterless fluids for pc 'water' cooling... most of the stuff that springs to mind for custom loops is distilled water + additives... i'm not sure whart the fluid used in AIOs is.
There were issues in the past with glycol damaging polycarbonate. A lot of testing was done on the subject that determined pure water was best for heat transfer. A little glycol is good, but a 50/50 automotive mix gave terrible heat transfer for a pc's temperature range. -I'm assuming you noticed the insane markup for pc coolant.
