the flyin' scotsman

Back in my racing days all coolant was banned as in the event of a leak its more lethal than oil on the track.

Heaven forbid you forgot to drain the system before fall/winter........cracked heads and blocks!

I've never had an issue with a water cooled engine with a 50/50 mix in street use.........all the way down to -40c. As to type of coolant it typical came down to price but most of my machines were not +20 year old Porsches.

A cylinder head gasket that lets go because of maintenance of the coolant system does seem a more expensive option than a regular coolant change. IMHO.

dr bob

Ramcram -- I've looked at the Evans coolant but not yet seen the need. So far anyway, the car gets two coolant replacements between belt changes. I treat it as a reason to stick my nose into places to look at things, check for leaks/seepage and the like. At least while living in the hot desert climate in Southern California, there was a noticeable difference in how well the system worked with different coolant concentrations. 25% worked better than 50%, for instance. So I was hesitant to try an almost-100% propylene glycol product like Evans. I know it won't boil over, but that doesn't mean it won't overheat in 100+ slow traffic driving with AC on full in a black car.

Malcolm -- my first serious introduction to Redline Water Wetter was in race-car radiators. It took SCCA a year or more to decide that it was an OK additive for track car cooling systems. Better than the "soluble oil" products we otherwise had to sneak into the systems. Plus detectable concentrations with the pink color when a draw sample was pulled. Eventually added two small mag-drive electric coolant pumps, pulled the little factory water-mover impeller from the TZ motor, and no longer needed anything beyond water in the system.

ramcram

You are absolutely correct, it won't protect you from something broken but most petrol engines would like to run hotter than 100C, just don't run hotter than the oil can tolerate.
What it does protect you from is, the hot day you describe, traffic jam, air on and the engine temp briefly rises above the phase change of water based coolant. Here you get the dreaded steam in the system, which doesn't cool, rapidly expands and expels the coolant all over the road and the engine temp hits 120C+ just as the traffic starts to move.
Synthetic coolant would just drop back to 100C and on you would go. Water based coolant would have you on the side of the road with the hod up and a worried frown.
Water is not good enough for internal combustion engines. In the early days, the Model A Ford etc were made such that they could boil all the way from LA to Les Vegas and back. Then our designers got smart and pressurised the cooling system. Better hoses, radiator cores and water pump seals nearly did it. So then they added liquid additives, presence of dissolved solids raised the boiling point again and this has pretty much done it, if all goes well!
Synthetic coolant is now factory fitted 'for life' in an increasing number of brands now.

Adk46

I must defend water, a special substance with peculiar properties. It is remarkable that such a light molecule (18) is liquid at room temperature. It has a higher heat capacity than any other liquid (unless you count pressurized ammonia), and requires an unusual amount of heat to vaporize. It is used in steam turbines not because it is cheap, but because there is nothing better. It even slows down neutrons to sustain a fusion reaction (and conveniently slowing the reaction if it boils).

Its melting point is inconvenient. It is a moderately strong chemical (we don't notice since we're made of water). We add extra stuff to our radiators to counter those problems, reducing cooling capacity in the process (not by much, and ignoring the effects of boiling temperature).

More profoundly, if ice did not float on top of water (a very peculiar behavior), life would have evolved very differently, if at all. Especially in Canada - go Penguins!

ramcram

Oh I'm very fond of water. I couldn't live without it! Penguins also. We have fairy penguins living wild just a half hours drive south of us. A bit longer if your not driving a 928.