Originally posted by fujiwara takumi
actually 50/50 can have you overheating.
just from scott's chart i know i would have to be nearly 60% antifreeze in the winter or i could lock up. and in the summer that same mix would see me popping my head.
If your cooling system is working properly, you should never see temps much over 200-210 F. I live in NC and I know the concentration in my Civic is pretty high - my hygrometer is pegged at -43 F, which is about 60%. I live in NC and it gets pretty damned hot here, but the Civic's gauge has never moved off the middle of the temp gauge. If you tend to overheat, check the functioning of your thermal switches - my mother's 89 civic (in PA) had all kinds of problems this summer, had to replace both fans and the thermal fan switch.
A chart on a regular prestone bottle I have says the best protection is at 70% coolant - -84 freezing, 276 boilover. But I believe above 70% is where the boiling point starts dropping.
You should NEVER run even near 100% water - it will not take long to corrode away your cooling system. I don't know why you would want to anyway, pure water will boil at around 220 F IIRC (under 1 atm pressure, at the normal 15 PSI radiator cap)