How long can a car stay in garage if temps drop below freezing

I pull the rad cap as that lets the water expand when it freezes. As one of the guys said, put an incandescent bulb under the block, or a small space heater with a fan and a shipping blanket over the motor.

As for Red Line water wetter, it is not a coolent, but an oil that is water soluble and helps with heat transfer and lubes the water system. Most racing cars use this as coolent is not allowed on tracks...