Block Heater is used to preheating the coolant in the engine to ensure the engine starts during extremely cold weather conditions. The engine block contains the heating element, which is powered by an electrical cord.
The Block Heater is an electrically-powered device used to pre-heat the coolant in the engine to start in severely cold weather, especially when the temperature drops to -15 degrees Celcius below. Most diesel vehicles typically use an engine block heater to keep the temperature from falling too low. Block heater warms the engine coolant and the engine, which removes the chill on the engine oil. This device is sometimes bolted into the block through an expansion plug hole or attached to the bottom radiator hose. Plugging in your automobile with a block heater before starting can reduce pollutants and improve the vehicle's fuel economy. However, the block heater does not need to be plugged in overnight since the heat it produced will be lost to the air, draining and wasting the charge in the battery.