Definition
Unrefined petroleum as it comes out of the ground, before processing. It is a mixture of hydrocarbons and other compounds that is separated and refined to produce aviation fuels, lubricating oils, hydraulic fluids, greases, and many other products used in aircraft operation and maintenance.
Plain English
Raw petroleum straight from the ground. It hasn't been processed yet. Refineries break it down and turn it into things like avgas, jet fuel, engine oil, and hydraulic fluid.
Context Anchor
Seen in discussions of aviation fuels, lubricants, petroleum products, and how aircraft fluids are made.
Derivation
Crude' comes from the Latin crudus, meaning raw or unprocessed. The word fits because crude oil is petroleum in its raw, untreated state, before refining turns it into useful products.
Why Pilots Care
Pilots do not put crude oil in an aircraft, but many aircraft fuels and oils begin as crude oil. Knowing the difference helps prevent confusing the raw source material with the finished aviation product.
Intuition Check
Crude oil does not mean dirty aviation fuel. It means raw petroleum before refining.
Example Sentence 1
Aviation gasoline and turbine engine fuel are both refined from crude oil, but through different processes.
Example Sentence 2
Aircraft engine oils are made from specially processed crude oil to handle high operating temperatures.