PCP pump cooling - where DIY gets... interesting

So, you wanna know if silicone oil and mineral oil can replace water as a thermal mass for your PCP pump? Well, I've got some bad news for you: those oils aren't exactly the best choices.

First off, both silicone oil and mineral oil have a much higher viscosity than water, which means they'll cause more resistance in your pump's seals. And trust me, you don't want that. O-rings (and other seals) can become damaged or even seize up when subjected to high pressures and viscosities.

Now, I know what you're thinking: "But won't the oils just... slow down the heat transfer?" Yeah, kinda. However, the increased viscosity also means they'll reduce the thermal conductivity of your pump's fluid, which is actually a bigger problem than the reduced cooling efficiency.

Water, on the other hand, has an excellent thermal conductivity and can efficiently transfer heat from your PCP pump to the surrounding air or another coolant.

So, what are you gonna do? Well, if you're looking for alternatives that won't harm your O-rings, you might consider using a proprietary, low-viscosity coolant designed specifically for liquid cooling systems. They usually have additives that reduce icing and corrosion concerns.

But hey, at least your PCP pump will be... lubricated?

TL;DR: Don't use silicone oil or mineral oil as thermal mass in your PCP pump. It's like putting diesel fuel in a Ferrari - just not gonna end well.