Was Castor Oil Really Used to Lubricate Jet Planes?

If you've heard that castor oil lubricates jet engines, you're not entirely wrong—but you're about 70 years out of date. This kitchen-cabinet staple did indeed keep aircraft engines running smoothly, just not the kind screaming across the sky today at 30,000 feet.

The golden age of castor oil in aviation was actually the early 20th century, when pilots had bigger problems than choosing the right lubricant—like staying alive.

The Rotary Engine Era

During World War I, most fighter aircraft used rotary engines, where the entire engine spun around a fixed crankshaft. These mechanical marvels generated serious heat and needed a lubricant that wouldn't break down. Enter castor oil, which had already proven itself in early automobiles.

Castor oil became the go-to lubricant because it maintained viscosity at high temperatures better than petroleum-based alternatives of the era. It was used almost universally in Allied rotary-engined aircraft throughout WWI. But this technological advantage came with an unforeseen side effect: castor oil is also a powerful laxative.

Pilots in open cockpits breathed in castor oil mist for hours. The result? Let's just say squadron bathrooms saw heavy traffic after missions. Some historians suggest this is why WWI pilots often wore silk scarves—not for style, but to cover their faces and filter the oily air.

The Synthetic Revolution

When jet engines emerged in the 1940s and 1950s, castor oil hit its limit. Early jets initially used mineral oil-based lubricants, but engineers quickly realized these new engines needed something entirely different. Jet turbines operate at temperatures and pressures that would turn castor oil into carbon deposits faster than you can say "catastrophic engine failure."

By the 1950s, military chemists developed the first synthetic Type I lubricants specifically for turbine engines. Modern jet engines use advanced polyolester-based synthetic oils with specialized additives that can handle:

• Temperatures ranging from -40°F to over 400°F
• Pressures exceeding 10,000 PSI
• Continuous operation for thousands of hours
• Compatibility with modern seals and materials

Today's commercial jets would never use castor oil. A Boeing 777 or Airbus A380 relies on lubricants engineered at the molecular level, meeting specifications like SAE AS5780 that didn't exist in castor oil's heyday.

Where Castor Oil Still Flies

Castor oil hasn't completely left aviation. It's still used in model airplane engines and some vintage aircraft restorations where authenticity matters. Racing enthusiasts also favor castor-based lubricants for high-RPM engines where conventional oils might fail.

So yes, castor oil lubricated aircraft engines—just not the kind with "fasten seatbelt" signs and in-flight movies. That WWI pilot who helped make castor oil famous? He'd be amazed to learn that the modern jet fuel used today burns cleaner than his engine oil ever did.