FYI straight distilled water out performs 50/50 mix.
Ethelene glycol based coolant actually inhabits the system to cool.
For decades racing teams use water with an additive to stop corrosion in the cooling system.
I think that's a little dangerous. How many people have had engine blocks or heads crack because that plain water froze? Yeah, maybe where you live it won't ever get that cold. But freakish stuff happens all the time.
