Ooops, Scott, he said -25 degrees, not +25.  50/50 is good down to -34.

From Wiki:
"Antifreeze was developed to overcome the shortcomings of water as a heat transfer fluid. In most engines, freeze plugs are placed in the engine block which could protect the engine if no antifreeze was present, or if the ambient temperature dropped below the freezing point of the antifreeze. If the engine coolant gets too hot, it might boil while inside the engine, causing voids (pockets of steam), leading to localized hot spots and the catastrophic failure of the engine. If plain water is used to cool an engine, it would promote galvanic corrosion. Proper engine coolant and a pressurized coolant system can help obviate the problems which make plain water incompatible with automotive engines. With proper antifreeze, a wide temperature range can be tolerated by the engine coolant, such as −34 °F (−37 °C) to +265 °F (129 °C) for 50% (by volume) propylene glycol diluted with water and a 15 psi pressurized coolant system.[1][2]"

YMMV,

Mr. BZ-still colder than a well digger's belt buckle

On Feb 3, 2011, at 3:30 PM, Scott Daniel - Turbovans wrote:
> ......................
> so if there is even 10 % old anti-frz in your coolant, 25 F shouldn't do any
> real damage.
> 
> 
>> We got down to minus 25 degrees (farenheit) the last couple days and I am
>> assuming the coolant in my 2.1 engine froze because I started it up now
>> that the weather is better and coolant was dripping pretty heavily from
>> the tin covering the passenger side head.
>> 
>> Anyone with experience related to this?  Is it likely just a freeze plug
>> that needs to be replaced now?   Are they easy to get to?  Could it be
>> anything else?
>> 
>> Thanks
>> Dave in Fort Collins