Editing Block heater (section)

==History==
An early example of pre-heating piston engines prior to start-up was in the 1930s in Northern Canada, where aviators flew with flight engineers who were responsible for preparing the [[radial engine]]s for shutdown and startup to reduce the effects of subzero temperatures. The flight engineer was responsible for draining the oil into buckets at night, and preheating the engine and buckets of oil using a blanket wrapped around the engine and a device known as a blow pot – essentially a [[kerosene]] jet-heater used for several hours prior to flight.<ref>{{cite web |title=Bent Props & Blow Pots |url=http://www.harbourpublishing.com/title/BentPropsBlowPots |website=www.harbourpublishing.com |access-date=30 August 2019 |language=en |archive-date=31 January 2020 |archive-url=https://web.archive.org/web/20200131073737/http://www.harbourpublishing.com/title/BentPropsBlowPots |url-status=dead }}</ref>

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 [[Winter Campaign of 1941–42|1941 winter campaign]] in the Soviet Union. A captured Soviet airman showed them how pouring aviation fuel into the aircraft's oil sump would thaw the oil. Another solution, also learned from the Soviets, was to ignite fuel in the space around the engine.<ref>{{Cite book
  |last=Kaplan
  |first=Philip
  |year=2007
  |page=118
  |title=Fighter Aces of the Luftwaffe in World War WWII
  |location=Auldgirth, Dumfriesshire, UK
  |publisher=Pen & Sword Aviation
  |isbn=978-1-84415-460-9
}}</ref>

An early automotive use was the "head bolt heater", invented by [[Andrew Freeman (inventor)|Andrew Freeman]] in the United States and patented on 8 November 1949.<ref name="Anchorage"/><ref name=Freeman>{{Cite web |url=http://www.prairiepublic.org/radio/dakota-datebook?post=6116 |title=Headbolt Heaters |access-date=2011-03-21 |archive-url=https://web.archive.org/web/20150721232350/http://www.prairiepublic.org/radio/dakota-datebook?post=6116 |archive-date=2015-07-21 |url-status=dead }}</ref><ref name=Patent_49>{{US patent reference| number = 2487326 |y= 1949 |m= 11 |d= 08 |inventor= A. L. Freeman |title= Electric Internal-Combustion Engine Head Bolt Heater }}</ref> These early heaters replaced one of the engine's head bolts with a hollow, threaded shank containing a resistive heating element.<ref name=Patent_49/><ref name=Patent_51>{{US patent reference |number= 2611066|y= 1952 |m= 09 |d= 16 |inventor= A. L. Freeman |title= Electric Head Bolt Heater for Internal-Combustion Engines }}</ref> Before the block heater was introduced, people used a variety of methods to warm engines before starting them, such as pouring hot water on the engine block or draining the engine's oil for storage inside overnight. Some even shoveled embers underneath their vehicle's engine to obtain the same effect.<ref name=Freeman/>