Block heater

Residential overnight street parking may not allow an extension cord to cross a public sidewalk.

However, the savings in fuel generally outweigh this cost, especially if a timer is used to limit the heating period to about 4 hours before the expected start time.

[1] Some cars pump hot coolant from the cooling system into a 3-litre insulated thermos-style reservoir at shutdown, where it stays warm for several days.

[7] Block heaters are frequently used in regions with cold winters such as the northern United States, Canada, Russia and Scandinavia.

[10] During World War II, German pilots could not stop the oil freezing in the engines of their Messerschmitt Bf 109 planes because of the extreme cold first experienced in the 1941 winter campaign in the Soviet Union.

[11] An early automotive use was the "head bolt heater", invented by Andrew Freeman in the United States and patented on 8 November 1949.

[1][12][13] These early heaters replaced one of the engine's head bolts with a hollow, threaded shank containing a resistive heating element.