I put the Evans stuff in my Alpine motor right after I rebuilt it several years ago, thinking I'd use it to preserve the motor. BAD IDEA. Despite having a re-cored and expanded radiator and the advantage of spotlessly clean cooling passages in the motor, the car ran enormously hot - scary hot - so much so that I was concerned about warping the head. After a few runs I drained it out and went to 50/50 Prestone antifreeze ... the car dropped right back into the normal range and hasn't varied out of that since. That oil simply doesn't have the physical ability to absorb and release the heat generated by these motors.
Oh, and if anyone wants to try using the Evans crap, I kept it when I drained it, so you're welcome to it, free of charge. Having paid silly money to buy the junk I didn't have it in my heart to toss it out, so maybe someone can make use of it in some unimportant vehicle.
I was gonna comment to say the same thing, though I have never personally used it.
It has a substantially lower thermal conductivity compared to water and though it boils at a much higher temp than even glycol, its ability to cool is perhaps half as good as water.
I have a acquaintance that put Evans in a hot-rodded flathead ford and it would not run below 260 degrees F at idle.
This would not be a huge problem (and he didnt mind it) since the vapor pressure with this stuff at that temperature is pretty low.
The big issue was that the thermostat would open up at 215 degrees F and then it would rise till the radiator had enough capacity (due to higher temp differential) to cool it down.
The result was that idling it would run 260 or so and then running down the road at speed it would run down closer to the thermostats temp.
The poor temp control made the engine tuning all over the place with a 60 degree range in coolant temp depending on conditions.
If you could buy a 260 or 275 degree thermostat then this would be alot less of an issue, but at those temps, you have to start worrying about oil degredation.