The engine coolant heater, if available, can help in cold weather conditions at or below 0°F (-18°C) for easier starting and better fuel economy during engine warm-up. Plug in the coolant heater at least four hours before starting the vehicle.
Caution: Plugging the cord into an ungrounded outlet could cause an electrical shock. Also, the wrong kind of extension cord could overheat and cause a fire. You could be seriously injured. Plug the cord into a properly grounded three-prong 110-volt AC outlet. If the cord will not reach, use a heavy-duty three-prong extension cord rated for at least 15 amps.
The length of time the heater should remain plugged in depends on several factors. Ask a dealer/retailer in the area where you will be parking the vehicle for the best advice on this.