Sierra is Propylene Glycol but aqueous, meaning it mixes with water and has a similar boiling point as water based coolants.
Sierra actually works well when converting to the waterless AND non-aqueous coolant I am using and was recommended by many here in S-CA: Evans NPG+.
I posted about it a couple of times since I converted.
Evans NPG+ is Propylene Glycol (like Sierra), but doesn't like water AND has a boiling point of 375* !
You may think coolant temps never get that high, why bother...
But what matters is the source of the heat, the cylinder walls.
They are much hotter than water's boiling point.
A layer of boiling water around the walls is obviously very inefficient for heat transfer or cooling.
The Evans stuff doesn't boil and actually transfers heat right at the source.
No corrosion, improves heat transfer, lubricates and flows better than regular coolant mix, the radiator stays clean, you can lower the pressure and hoses need less replacing.
Putting water inside a cast iron engine makes no sense when this stuff is available and works and is guaranteed for the life of the engine without replacing.
I used this coolant for 3 years now and never go back. I know of many people who converted all their cars to this stuff.
Very expensive (don't ask, still hurts) but after a few years you get more than your money back in return.
The engine seems to really like it, looking at the temp gauge during the hot summer months here in the desert.
Before it seemed more like a pressure cooker slowly eating up the iron and radiator from the inside out, leaving deposits to be cleaned regularly.
Anyway, don't take my word for it - there's gotta be plenty of positive experiences on various forums on the net.
You may also find the usual skeptics who have never tried it and are turned off by the initial investment.
