Robert and David,
As you both likely know, the reason to NOT use regular Ethyl Glycol coolant, at least in unpressurized cooling systems, is because it FOAMS UP and gets sucked out of the radiator, thereby causing both overheating and a series mess.
Perhaps, the newer Pierce-Arrow cars can handle the Ethyl Glycol mixture because you Gents have pressurized systems.
I offer this information for the Greenhorns and not for the Old Hands.
I used both the Pencool and the Napa products with good cooling results and without boil-overs.
I also do a radiator flush every year or so and everything comes out looking clean, mostly clear and without rust.