Winterizing

Store the cooling system wet. Draining it and leaving the car empty dries the seals out, and they leak when you refill. That damages more cars over a winter than freezing does.

Which coolant to leave in it

If the car will not see freezing temperatures, leave the distilled water and Water Wetter in it and do nothing.

If it will, replace the water with something rated for the cold you expect:

Expected low	Use
Above freezing	Distilled water + Water Wetter, unchanged
Down to 0°F (-18°C)	VP Stay Frosty
Below 0°F (-18°C)	Glycol antifreeze, rated to -35°F (-37°C) at the manufacturer’s mix

Mix for your own climate rather than for the coldest number on the bottle.

Caution

Glycol is a track safety hazard and is not permitted in competition. If you store the car with it, drain the system completely and refill with distilled water and Water Wetter before the car runs again.

Doing the changeover

Draining and refilling is the same procedure as an ordinary coolant change, including burping the system afterwards. See Changing Coolant.

Capacity and the fluid specs are on the Fluids page.