Editing Castor oil (section)

===Early aviation and aeromodelling===
[[File:Le Rhone 9C.jpg|thumb|right|World War I aviation [[rotary engines]] used castor oil as a primary lubricant, mixed with the fuel]] 
Castor oil was the preferred lubricant for [[rotary engines]], such as the [[Gnome et Rhône|Gnome engine]] after that engine's widespread adoption for aviation in Europe in 1909. It was used almost universally in rotary-engined Allied aircraft in [[World War I]]. Germany had to make do with inferior ''[[ersatz]]'' oil for its rotary engines, which resulted in poor reliability.<ref>{{cite book |last= Guilmartin |first= John F. Jr. |title= Two Historians in Technology and War |year= 1994 |publisher= United States Army War College, Strategic Studies Institute |isbn= 978-1428915220 |page= 10 |chapter= Technology and Strategy: What Are the Limits?}}</ref><ref>{{cite book |last= Fisher |first= Suzanne Hayes |title= The European Powers in the First World War: An Encyclopedia |year= 1999 |publisher= Taylor & Francis |isbn= 978-0815333517 |page= 10 |chapter= Aircraft, production during the war |editor-first1= Spencer C. |editor-last1= Tucker |editor-first2= Laura Matysek |editor-last2= Wood |editor-first3= Justin D. |editor-last3= Murphy }}</ref><ref>{{cite book |title= Tariff Information Surveys on the Articles in Paragraphs 44 and 45 of the Tariff Act of 1913 |year= 1921 |author= U.S. Tariff Commission |page=40 |publisher= Government Printing Office |location= Washington, D.C. |author-link= United States Tariff Commission }}</ref>

The [[methanol]]-fueled, two-cycle, [[Glow plug (model engine)|glow-plug engines]] used for aeromodelling, since their adoption by [[model airplane]] hobbyists in the 1940s, have used varying percentages of castor oil as lubricants. It is highly resistant to degradation when the engine has its fuel-air mixture leaned for maximum engine speed. Gummy residues can still be a problem for aeromodelling powerplants lubricated with castor oil, however, usually requiring eventual replacement of [[ball bearing]]s when the residue accumulates within the engine's bearing races. One British manufacturer of [[sleeve valve]]d four-cycle model engines has stated the "varnish" created{{fact|date=January 2025}}<!-- many classical sources talk about the absence of film --> by using castor oil in small percentages can improve the pneumatic seal of the sleeve valve, improving such an engine's performance over time.