Ideal coolant ratio?

If you run Green (I do... in my opinion it's better than the red garbage) YOU HAVE TO FULLY FLUSH THE RED OUT BEFORE YOU PUT THE GREEN IN.

 

I think this thread has ended . . . but, just thought I'd mention a real life case for changing the rad cap. I had a motorcycle that was not leaking radiator fluid, but would overheat under extreme conditions. Extreme in this case being high speed cornering while going up mountain roads. After much work, research and frustration, it turned out to be the rad cap. It wasn't leaking fluid, but was not properly pressuring the system and was allowing air to enter. The air ended up in the water pump, causing cavitation (the pump impeller spins in air and does not move fluid). Replacing the rad cap fixed the issue. So, last weekend I replaced the radiator in my Tacoma and also replaced the rad cap, just to be safe. It's cheap insurance and should be done every few years.