Coolant

[Immortality]

That is true but glycol also reduces the efficiency of the coolant to transfer heat so you win a little by increasing the boiling point a couple of degrees but loose efficiency and the engine should never operate at such a high temperature.

The increase in cooling system pressure provides most of the increase in boiling point.

But great marketing makes people believe you must run anti-freeze in hot climates when it simply isn't required.

So your V6 runs at 20psi which means with plain water the boiling point of the cooling system is 260°F or 126°C. If your engine gets this hot there are some serious problems. If you run anit-freeze (at 50%) that increases to 135°C or 7% over straight water, yippy but at those temps you've probably fucked the motor regardless so I wouldn't be going there.

Here is some interesting reading about the effects of glycol in cooling systems, it's quite intensive reading.

Ethylene Glycol Heat-Transfer Fluid Properties

Properties like freezing point, viscosity, specific gravity and specific heat of ethylene glycol based heat-transfer fluids, or brines.

www.engineeringtoolbox.com

But to quote from the above page,

Note! The specific heat of ethylene glycol based water solutions are less than the specific heat of clean water. For a heat transfer system with ethylene glycol the circulated volume must be increased compared to a system only with water.

In a 50% solution with operational temperatures above 36 oF the specific heat capacity is decreased with approximately 20%. The reduced heat capacity must be compensated by circulating more fluid.

Note! The density of ethylene glycol is higher than water - check the specific gravity (SG) table above, so the net impact on the heat transport capacity is reduced. Example - the specific heat of an ethylene glycol water solution 50% / 50% is 0.815 at 80 oF (26.7 oC). Specific gravity at the same conditions is 1.077. The net impact can be estimated to 0.815 * 1.077 = 0.877.

Now back in the linked page above at 80°C - 100°C at 50% glycol the specific heat is about .88 or 12% less efficient than straight water and it gets worse as the %age of glycol increases.

Glycol based coolants are expensive, do you really need it? TBH, I don't care, it's not my money but don't believe all the marketing hype about anti-freeze. What you do need is corrosive inhibitors.

edit: add context

Holden fitted a 195°F/91°C thermostat to your 3.8 V6 motor (I take this to mean that this is the engine temp Holden wants the motor to operate), Holden set the low speed thermofan to turn on at 104°C and the high speed thermofan at 109°C, this tells me Holden doesn't really want the engine to get above this temp and still a fair margin to 126°C before you reach the boiling point.

 

[Jasminka]

Yes I am aware of the specific heat issue, which affects how much heat the liquid can carry away. The best specific heat happens to be water and ammonia - simple molecules and everything longer like ethylene glycol is worse. I would never use that "waterless coolant" stuff which is very expensive. The company making it does not divulge the specific heat anywhere.

 

[Fu Manchu]

Wait. Why aren’t we just using the coolant designed for the car?

 

[Immortality]

Wait. Why aren’t we just using the coolant designed for the car?

Why do you use coolant?

 

[greenacc]

Wait. Why aren’t we just using the coolant designed for the car?

Mostly because of people wanting to sell you alternative products with some good sales tactics!
How often do commodores overheat unless a radiator/cap/hose bursts?

 

[Immortality]

Wait. Why aren’t we just using the coolant designed for the car?

We are but why do we use glycol based coolants?

Not sure why the other user mentioned waterless coolant as it wasn't relevant to the discussion.